2003 CRC/FYNU - CP3 - Université catholique de Louvain

Transcription

I.I.S.N.
U.C.L.-Louvain-la-Neuve
CYCLONE
Rapport d'activité 2003
INSTITUT INTERUNIVERSITAIRE DES SCIENCES NUCLEAIRES
UNIVERSITE CATHOLIQUE DE LOUVAIN
RAPPORT SCIENTIFIQUE
DE L'UTILISATION DES CYCLOTRONS
ET DES ACTIVITES DE L'INSTITUT
DE PHYSIQUE NUCLEAIRE
2003
Institut de Physique Nucléaire
et Centre de Recherches du Cyclotron
Université catholique de Louvain
Chemin du Cyclotron, 2
B-1348 Louvain-la-Neuve
Belgique
Tél. 010/47.32.73 - 47.29.98
Téléfax : 010/45.21.83
TABLE DES MATIÈRES
I. RECHERCHES AUPRÈS DES ACCELÉRATEURS DE LOUVAIN-LA-NEUVE ..... 1
1. ASTROPHYSIQUE NUCLÉAIRE / NUCLEAR ASTROPHYSICS............................................................1
1.1. UPDATED BIG BANG NUCLEOSYNTHESIS AND ABUNDANCE OF LIGHT ELEMENTS ........................1
1.2. STUDY OF THE 19Ne(p,γ)20Na REACTION USING THE RECOIL SEPARATOR ARES .................................3
1.2.1. Beam related measurements ......................................................................................................................4
1.2.2. Results .......................................................................................................................................................4
1.3. THE 18F(α,p)21Ne REACTION : A KEY TO UNDERSTANDING NEUTRON PRODUCTION IN
R-PROCESS SITES ................................................................................................................................................5
2. NOYAUX EXOTIQUES / EXOTIC NUCLEI ................................................................................................7
2.1.STUDY OF THE PROTON DRIP LINE NUCLEUS 11N BY 10C+p RESONANT ELASTIC SCATTERING.......7
2.2. SPECTROSCOPY OF 7He BY THE 9Be(6He,7He)8Be TRANSFER REACTION..................................................9
2.3. SPECTROSCOPY OF 5H BY THE 7Li(6He,5H)8Be TRANSFER REACTION ....................................................10
2.4. SUB-BARRIER FUSION STUDY OF LIGHT NUCLEI : 7Be + 238U ..................................................................12
2.5. MEASUREMENT OF THE 6He β-DELAYED α+d EMISSION BRANCHING RATIO ....................................13
3. RÉACTIONS ET STRUCTURES NUCLÉAIRES / REACTIONS AND NUCLEAR STRUCTURES ..15
3.1. PROPERTIES OF NEUTRON EMISSION IN FISSION PROCESSES INDUCED BY 20Ne+159Tb AND
20
Ne+169Tm REACTIONS BETWEEN E + 8 AND 16 MeV/NUCLEON............................................................15
3.1.1. Introduction .............................................................................................................................................15
3.1.2. Details on the experimental set-up and procedures of the data analysis .................................................16
3.1.3. Neutron multiplicity distributions as a function of fission-fragment mass partition ................................16
3.1.4. Effects of the CN recoil velocity on the neutron angular distribution......................................................18
3.1.5. Conclusion ...............................................................................................................................................20
3.2. ISOTROPY OF THE NEUTRON EMISSIONS IN AND OUT OF THE REACTION PLANE AND THE
PARAMETRIZATION OF THEIR ANGULAR DISTRIBUTION......................................................................21
3.2.1. Isotropy of the neutron emission in and out of the reaction plane ...........................................................21
3.2.2. Effects of the CN recoil velocity on the neutron emission in and out of the reaction plane .....................23
3.3. NEUTRON-SKIN EFFECTS IN THE MIRROR REACTIONS 58Ni + 122Sn AND 64Ni + 116Sn BETWEEN 6
AND 7 MeV/NUCLEON ......................................................................................................................................24
3.3.1. Introduction .............................................................................................................................................24
3.3.2. Experimental setup ..................................................................................................................................24
3.3.3. Experimental results ................................................................................................................................25
3.3.4. Simulations ..............................................................................................................................................26
3.3.5. Conclusion ...............................................................................................................................................27
3.4. PRODUCTION OF NEUTRAL AND LIGHT CHARGED PARTICLES IN THE PROTON AND ALPHA
INDUCED REACTIONS ON NATSI BETWEEN 20 AND 65 MeV ..................................................................28
3.5. STUDY OF PROTON-INDUCED FISSION OF ACTINIDE NUCLEI BETWEEN 20 AND 80 MeV
BOMBARDING ENERGIES................................................................................................................................32
3.5.1. Introduction .............................................................................................................................................32
3.5.2. Experimental setup ..................................................................................................................................32
3.5.3. Fission fragment mass distributions ........................................................................................................33
3.5.4. Prospectives.............................................................................................................................................34
4. REACTIONS INDUITES PAR DES NEUTRONS / REACTIONS INDUCED BY NEUTRONS ...........35
4.1. MEASUREMENT OF MICROSCOPIC CROSS SECTIONS IN FAST NEUTRON INDUCED REACTIONS
(En =25 – 65 MeV) ON BISMUTH AND NATURAL URANIUM......................................................................35
4.2. LIGHT CHARGED PARTICLE PRODUCTION INDUCED BY FAST NEUTRONS (En = 25 – 65 MeV) ON
NAT
Fe .....................................................................................................................................................................37
5. PHYSIQUE DES NANOSTRUCTURES / NANOSTRUCTURE PHYSICS .............................................39
5.1. NANOSCOPIC SUPERCONDUCTING SLAB IN STATIC ELECTRIC AND MAGNETIC FIELDS ..............39
5.1.1. Electrostatic potential in a covariant framework ....................................................................................39
5.1.2. Paraconductivity......................................................................................................................................39
5.1.3. Four-fermion couplings ...........................................................................................................................39
i
5.2. VORTEX MATTER IN LEAD NANOWIRES .....................................................................................................40
5.2.1. Introduction .............................................................................................................................................40
5.2.2. Analysis of the experiments......................................................................................................................40
5.2.3. Comments and conclusions......................................................................................................................42
5.3. TRACK ETCHING IN POLYMERS.....................................................................................................................42
5.3.1. Introduction .............................................................................................................................................42
5.3.2. Activities during year 2003......................................................................................................................43
5.3.3. Activities forecast for year 2004 ..............................................................................................................44
6. RADIOBIOLOGIE / RADIOBIOLOGY.......................................................................................................45
6.1. INDUCTION DE L'APOPTOSE DANS DES CELLULES NORMALES ET TUMORALES PAR LES
NEUTRONS RAPIDES : ETUDE DES MECANISMES CONCERNES ET MODULATION
PHARMACOLOGIQUE.......................................................................................................................................45
7. ACCÉLÉRATEUR VAN DE GRAAFF / VAN DE GRAAFF ACCELERATOR .....................................47
7.1.1. Introduction .............................................................................................................................................47
7.1.2. Analysis with a 1 MeV He beam ..............................................................................................................47
7.1.3. Analysis with 2.2. to 3.2 MeV proton beam energies ...............................................................................49
7.1.4. Conclusions .............................................................................................................................................51
8.
RECHERCHES MENEES PAR LE CENTRE DES RADIATIONS SPATIALES (CSR) /
RESEARCHES AT THE CENTER FOR SPACE RADIATIONS (CSR)...............................................52
8.1. RADIATION ENVIRONMENT RESEARCH WITH MULTIPLE MONITORS................................................52
8.2. CLASSIFICATION OF SOURCES OF SINGLE EVENT EFFECTS IN SPACE ...............................................53
8.3 MEASUREMENT OF ANGULAR VELOCITY USING EUV IMAGES OF THE EARTH'S
PLASMASPHERE ................................................................................................................................................53
8.4. VLF WAVE ANALYSIS FROM THE OBSERVATIONS OF THE WHISPER INSTRUMENT.......................54
8.5. CONSTRUCTION OF THE ENERGETIC PARTICLE TELESCOPE (EPT) .....................................................55
II. RECHERCHES AUPRÈS D’AUTRES ACCELÉRATEURS...................................... 58
1. CHORUS : Production de particules charmées induites par des neutrinos ν µ ..........................................58
2. CMS...................................................................................................................................................................58
2.1. ACTIVITES LIEES A LA CONSTRUCTON DU TRACKER "AVANT" ...........................................................58
2.1.1. Qualification des senseurs au silicium et sensibilité aux dégâts radiatifs ...............................................59
2.1.2. Conception des circuits de refroidissement des pétales...........................................................................66
2.1.3. Construction de générateurs de liquide froid ..........................................................................................67
2.1.4. Tests de circuits hybrides.........................................................................................................................68
2.1.5. Temperature distribution tests on the petals of the CMS-Tracker End Caps...........................................71
2.1.6. CMS Tracker Petal and Module tests ......................................................................................................73
2.2. ACTIVITES LIEES A LA SELECTION ET A LA RECONSTRUCTION DES EVENEMENTS.......................76
2.2.1. HLT Steering Code Prototype..................................................................................................................76
2.2.2. Standard model Higgs boson study : WW decays ....................................................................................77
2.2.3. Multi-object trigger scheme, an example.................................................................................................79
2.4.4. Development of a computer cluster .........................................................................................................80
2.3. ACTIVITES LIEES A L’ETUDE DES INTERACTIONS DE PHOTONS DE HAUTE ENERGIE AU LHC ....81
2.3.1. Monte Carlo event generation and simulation in CMS detector..............................................................81
2.3.2. Studies of the triple gauge coupling γWw in photoproduction at the LHC .............................................83
2.3.3. Simulation of the proton transport in the LHC beam-line ......................................................................85
2.3.4. Two-photon production of the lepton pairs at the LHC ..........................................................................85
2.4. PHENOMENOLOGIE AU LHC............................................................................................................................87
2.4.1. Techniques numériques pour le calcul de diagrammes de Feynman à une boucle..................................87
2.5. PHYSIQUE THEORIQUE.....................................................................................................................................88
2.5.1. Problèmes de quantification et compactifications de théorie des cordes.................................................88
2.5.2. Topologie et quantification en théories de jauges à basses dimensions ..................................................89
2.5.3. Nonperturbative approaches to two-dimensional gauge theories............................................................90
2.5.4. Neutrino pair production in background electromagnetic fields and anomalous couplings....................91
ii
3.
HARP : PRODUCTION DE HADRONS DANS LES COLLISIONS PROTON-NOYAU VERS
GEV/C............................................................................................................................................................92
4. MICE : MUON IONIZATION COOLING EXPERIMENT .......................................................................92
5. ALEPH..............................................................................................................................................................93
5.1. CHARGED HIGGS SEARCHES AT ALEPH ......................................................................................................93
5.2. UNE EXTENSION MINIMALE DU SECTEUR SCALAIRE :LE MODELE A UN SINGULET.......................94
5.3. SEARCH FOR A HIGGS BOSON DECAYING INTO W PAIRS AT LEP .........................................................96
5.4. GRANTING THE ACCESS TO ALEPH DATA FOR THE FUTUR ...................................................................98
6 . RD39 COLLABORATION ............................................................................................................................99
7. ZEUS COLLABORATION ..........................................................................................................................101
8.
PRECISION MEASUREMENT OF SINGLET µP CAPUTRE IN HYDROGEN –
PSI EXPERIMENT R-97-05......................................................................................................................103
8.1. OVERVIEW.........................................................................................................................................................103
8.2. PROGRESS 2003.................................................................................................................................................104
8.3. COMMISSIONING RUN ....................................................................................................................................105
8.3.1. Hydrogen system....................................................................................................................................106
8.3.2. Detectors and DAQ................................................................................................................................106
8.3.3. Data analysis and first results ...............................................................................................................107
III. INSTRUMENTATION ET DÉVELOPPEMENTS TECHNIQUES ....................... 109
1. ON-LINE RESULTS WITH LISOL LASER ION SOURCE....................................................................109
1.1. INTRODUCTION................................................................................................................................................109
1.2. EXPERIMENTS WITH STABLE 58Ni BEAM ...................................................................................................109
IV. EXPLOITATION ET DÉVELOPPEMENTS DES CYCLOTRONS ...................... 111
1. INTRODUCTION..........................................................................................................................................111
2. OPERATION .................................................................................................................................................111
3. RESEARCH AND DEVELOPMENT..........................................................................................................114
3.1. DEVELOPMENT AND PRODUCTION OF RADIOACTIVE ION BEAMS (RIB)..........................................114
3.1.1. Operation with RIB................................................................................................................................114
3.1.2. First experiment using a 10C beam ........................................................................................................115
3.1.3. First experiment using a 15O beam ........................................................................................................115
3.1.4. Increased 18F average intensity using a dual trap .................................................................................115
3.2. ADDITIONAL TESTS FOR 39AR MEASUREMENTS......................................................................................115
3.3. CYCLONE 44 ......................................................................................................................................................116
3.3.1. First full experiment with RIBs at CYCLONE44 (19Ne).........................................................................116
3.3.2. Control system development ..................................................................................................................116
3.3.3. Other developments ...............................................................................................................................118
3.4. ECR ION SOURCE DEVELOPMENT ...............................................................................................................118
3.4.1. New 23Na beam for CYCLONE44 ..........................................................................................................118
3.4.2. New ion cocktail with SCAMPI..............................................................................................................119
3.5. TECHNOLOGICAL APPLICATONS.................................................................................................................119
3.5.1. Two successful runs of 7Be for applications ..........................................................................................119
3.5.2. Heavy ion irradiation facility.................................................................................................................119
3.5.3. Neutron Irradiation Facility (NIF) ........................................................................................................121
3.5.4. Proton Irradiation Facility (LIF)...........................................................................................................121
3.6. MISCELLANEOUS.............................................................................................................................................121
iii
V. LOGISTIQUE ................................................................................................................. 122
1. MECANIQUE ................................................................................................................................................122
2. BUREAU DE DESSIN...................................................................................................................................123
3. ELECTRONIQUE .........................................................................................................................................123
3.1. ATELIER D'ELECTRONIQUE : ACTIVITES POUR CMS ..............................................................................123
3.1.1. FHIT ......................................................................................................................................................123
3.1.2. Petal assembly and Burn-in ...................................................................................................................123
3.1.3. L'atelier d'électronique est impliqué quotidiennement dans les diverses activités du groupe CMS.......124
3.2. AUTRES ACTIVITES .........................................................................................................................................124
4. LOGISTIQUE INFORMATIQUE...............................................................................................................124
4.1. GESTION DU PARC INFORMATIQUE............................................................................................................124
4.2. DEVELOPPEMENTS POUR CMS.....................................................................................................................125
VI. ANNEXES ...................................................................................................................... 127
1. PUBLICATIONS DANS DES REVUES......................................................................................................127
2. COMMUNICATIONS ET PARTICIPATIONS A DES CONGRES........................................................130
3. RAPPORTS INTERNES...............................................................................................................................134
4. SEMINAIRES ET SEJOURS DE RECHERCHE ......................................................................................134
4.1. SEMINAIRES ET COURS DE 3è CYCLE..........................................................................................................134
4.2. SEMINAIRES ET COURS DONNES A L'EXTERIEUR ...................................................................................134
4.3. SEJOURS DE RECHERCHES A L'ETRANGER ...............................................................................................135
4.4. DIVERS ...............................................................................................................................................................135
5. PROMOTION ET VULGARISATION DES SCIENCES .........................................................................135
5.1. CAMPAGNES DE VOLS PARABOLIQUES DE L’ESA ..................................................................................135
5.2. DOSSIERS DIDACTIQUES................................................................................................................................136
5.3. FESTIVAL DES SCIENCES, MAGAZINE SCIENCE INFUSE ET CONFERENCES.....................................136
6. DIPLOMES ....................................................................................................................................................137
6.1. THESES DE DOCTORAT ..................................................................................................................................137
6.2. DIPLOMES D’ETUDES APPROFONDIES OU SPECIALISES (DEA, DES) ..................................................137
6.3. MEMOIRES DE LICENCE .................................................................................................................................137
7. PERSONNEL .................................................................................................................................................137
7.1. INSTITUT DE PHYSIQUE NUCLEAIRE..........................................................................................................137
7.2. CENTRE DE RECHERCHES DU CYCLOTRON..............................................................................................139
iv
I. RECHERCHES AUPRÈS DES ACCÉLÉRATEURS
DE LOUVAIN-LA-NEUVE
1. ASTROPHYSIQUE NUCLÉAIRE / NUCLEAR ASTROPHYSICS
1.1. Updated Big Bang nucleosynthesis and abundance of light elements
C. Angulo (Centre de Recherches du Cyclotron, Université catholique de Louvain, Louvain-la-Neuve, Belgium);
P. Descouvemont, A. Adahchour (PNTPM, ULB, Brussels, Belgium); A. Coc (CSNSM, CNRS/IN2P3/UPS,
Orsay Campus, France); E. Vangioni-Flam (IAP/CNRS, Paris, France)
Résumé : A partir des observations des anisotropies du rayonnement du fond cosmologique, le satellite WMAP
a déterminé la densité baryonique de l’Univers, Ωbh2, avec une précision sans précédent. Une
diminution des incertitudes des taux de réactions impliqués dans la nucléosynthèse du Big Bang
Standard, utilisés eux aussi pour déterminer Ωbh2, est donc nécessaire pour comparer les résultats de
ces deux méthodes sur ce paramètre cosmologique fondamental. Dans ce but, nous avons réalisé une
nouvelle compilation comprenant les réactions nucléaires impliquées dans la nucléosynthèse du Big
Bang, en utilisant, pour la première fois, la théorie de la matrice R pour ajuster les données aux
basses énergies ainsi qu’un traitement des erreurs sur des bases statistiques. Nous avons combiné ces
résultats avec les observations de WMAP pour déduire les abondances primordiales des éléments
légers (D, 3He, 4He, 7Li) et nous les avons comparés avec les observations spectroscopiques. Des
importantes divergences sont obtenues pour le 7Li. L’origine de cette divergence (observationnelle,
nucléaire ou plus fondamentale) reste inconnue. Le rôle des réactions 7Be(d,p)24He et 7Be(d,α)5Li,
négligées jusqu’au maintenant, est discuté.
Standard Big-Bang Nucleosynthesis (SBBN) has been the only method to evaluate the baryonic density
in the Universe, by comparing observed and calculated light-element abundances [1,2] (4He, D, 3He and 7Li).
However, the study of Cosmic Microwave Background (CMB) anisotropies has provided very recently a new
tool for the precise determination of the baryonic density, which can be compared to the results obtained from
SBBN. The precision on the determination of the baryonic density of the universe, Ωbh2, from the CMB has been
drastically improved with the WMAP satellite [3] (Ωbh2 = 0.0224 ± 0.0009, as usual, Ωb is the ratio of the
baryonic density over the critical density and his the Hubble constant in units of 100 km·s-1·Mpc-1). It is therefore
crucial to reduce the uncertainties on the thermonuclear rates, which is the main input in SBBN.
Compilations of thermonuclear reaction rates for astrophysics, containing the main reactions of SBBN,
have been initiated by W. Fowler and his collaborators. The last version [4] of this compilation was published in
1988 but it is now partially superseded by the NACRE compilation [5]. Compilations concerning specifically
SBBN reaction rates have been performed by Smith, Kawano, and Malaney [6] (SKM) and Nollett and Burles [7]
(NB). The SKM analysis used polynomial expansions for the cross sections, and the uncertainties on the rates
were in general only estimated by allowing the S-factor limits to encompass all existing data, a prescription also
found in some reactions covered by NACRE. From the statistical point of view, the rate uncertainties are better
defined in the NB compilation than in SKM or NACRE, but the astrophysical S-factors of NB are fitted by
splines which have no physical justification. A practical difficulty with the NB compilation is that the rates are
not provided because, by construction, they cannot be disentangled from the Monte-Carlo calculations.
In a recent work [8], we have compiled and analyzed low-energy cross sections involved in the BBN in
the R-matrix framework [9], providing more rigorous energy dependence based on Coulomb functions. A second
goal of our work is a careful evaluation of the uncertainties associated with the cross sections and reaction rates
using standard statistical techniques [10]. Since the completion of the NACRE compilation, several new data have
come available and are included to update the reaction rates. This new BBN compilation [8] provides 1-σ
statistical limits for each of the 10 rates: 2H(p,γ)3He, 2H(d,n)3H, 2H(d,p)3H, 3H(d,n)4He, 3H(α,γ)7Li, 3He(n,p)3H,
3
He(d,p)4He, 3He(α,γ)7Be, 7Li(p,α)4He and 7Be(n,p)7Li. The two remaining reactions of importance, n ↔ p and
1
H(n,γ)2H come from theory and are unchanged with respect to previous works. Using these updated BBN
compilation, we have performed a Monte-Carlo calculation using Gaussian distributions with parameters
provided by this new compilation of reactions and we have calculated the 4He, D, 3He, and 7Li yield range as a
function of the baryon over the photon ratio η or Ωbh2 [11].
1
Figure 1 displays the resulting abundance limits from SBBN calculations compared to primordial ones
deduced from observations together with the Ωbh2 WMAP range. There is a very good agreement for deuterium
as the baryonic density deduced from D/H observations in cosmological clouds and SBBN calculations overlap
the Ωbh2 WMAP range. The exact convergence between these two independent methods reinforces the
confidence in the deduced Ωbh2 value. The agreement for 4He is not as good but remains acceptable while 3He is
not considered here because of its uncertain galactic rate of production and destruction. The 7Li abundances
measured in halo stars of the Galaxy was considered up to now as representative of the primordial abundance as
they display a plateau as a function of metallicity. However, when using the baryonic density from WMAP in
SBBN calculations, the resulting 7Li abundance is a factor of 3.4 larger than the most recent observational
determination of the 7Li primordial abundance [11]. If large observational bias or nuclear uncertainties can be
excluded, new physics has to be invoked. Recent theory that could affect BBN include the variation of the fine
structure constant, quintessence, modified gravity, leptons asymmetry,....
The right wing of the valley shaped 7Li SBBN abundance curve (Figure 1), is associated with 7Be
formation that further decays to 7Li. Hence reconciliation of SBBN, WMAP and 7Li observations by nuclear
physics can only come from 7Be production and destruction rates. In SBBN, these reactions are 3He(α,γ)7Be and
7
Be(n,p)7Li and are sufficiently well known to exclude this. However, other reactions which have been neglected
up to now have to be considered. This is the case of the 7Be(d,p)24He and 7Be(d,α)5Li reactions. The present rate
of 7Be + d comes from an estimate by Parker [12] based on experimental data above the laboratory energy Ed =
0.7 keV from an early work of Kavanagh [13]. If the actual rate were higher by a factor of about 100, the 7Li
disagreement would vanish (red dashed-dotted curves in Figure 1 correspond to factors 10 to 100).
Figure 1 : Abundances of 4He (mass fraction), D, 3He and 7Li (by number relative to H)
versus η or Ωbh2. Limits (1-σ) are obtained from Monte-Carlo calculations [11].
The yellow horizontal lines are primordial abundances deduced from
observational data. The vertical stripe are the (1-σ) Ωbh2 provided by WMAP[4].
For the red dashed-dotted line in the bottom panel: see text.
In view of the important physical implications of a confirmed SBBN and CMB (WMAP) strong
disagreement on 7Li, nuclear effects have to be excluded. The measurement of the 7Be + d cross section at SBBN
energies is thus of the greatest importance. An experiment has been performed in May 2004 at the CRC to
investigate 7Be + d reactions using the low-energy 7Be beam and a ∆Ε − Ε telescope detection system [14]. Data
analysis in ongoing.
2
This work has been supported by the PAI program P5/7 on Interuniversity Attraction Poles of the
Belgian-state Federal Services for Scientific, Technical and Cultural Affairs.
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
K.A. Olive, G. Steigman and T.P. Walker, Phys. Rep. 333 (2000) 389.
A. Coc, E. Vangioni-Flam, M. Cassé and M. Rabiet, Phys. Rev. D65 (2002) 043510.
D.N. Spergel et al., submitted to Astrophys. J., arXiv:astro-ph/030220 reprint.
G.R. Caughlan and W.A. Fowler, At. Data Nucl. Data Tables 40 (1988) 283.
C. Angulo et al., Nucl. Phys. A656 (1999) 3.
M.S. Smith, L.H. Kawano, and R.A. Malaney, Astrophys. J. S. 85 (1993) 219.
K.M. Nollett and S. Burles, Phys. Rev. D61 (2000) 123505.
P. Descouvemont, A. Adahchour, C. Angulo, A. Coc, E. Vangioni-Flam, At. Data Nucl. Data Tables, in
press.
A.M. Lane and R.G. Thomas, Rev. Mod. Phys. 30 (1958) 257.
Particle Data Group, K. Hagiwara et al., Phys. Rev. D66 (2002) 010001.
A. Coc, E. Vangioni-Flam, P. Descouvemont, A. Adahchour, C. Angulo, Astrophys. J. 600 (2004) 544.
P.D. Parker, Astrophys. J. 175 (1972) 261.
R.W. Kavanagh, Nucl. Phys. 18 (1960) 492.
C. Angulo, A. Coc, et al., proposal PH-203, CYCLONE PAC meeting of January 2003.
1.2. Study of the 19Ne(p,γ)20Na reaction using the recoil separator ARES
M. Couder, C. Angulo, E. Casarejos, P. Leleux, F. Vanderbist (Institut de Physique Nucléaire et Centre de
Recherches du Cyclotron, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
Résumé : La réaction 19Ne(p,γ)20Na est présente dans plusieurs chaînes de réactions liant le cycle CNO chaud
et le processu -rp dans la combustion hydrodynamique de l'hydrogène et de l'hélium. La force de la
résonance à 448 keV a été mesurée avec le séparateur de recul ARES. Une limite supérieure de 15
meV (90 % C.L.) a été obtenue. Ce résultat restreint légèrement une détermination préalable obtenue
à l'aide de méthodes différentes.
The 19Ne(p,γ)20Na reaction is of great astrophysical interest because it is involved in different chains
allowing the escape from the hot-CNO cycles [1]. In temperature domain of relevance in the environments of
interest, novae and X-ray bursts, the reaction rate is dominated by a resonant level at 448 keV above threshold, at
excitation energy of 2.643 MeV in 20Na.
Several investigations of the 19Ne(p,γ)20Na reaction were performed in Louvain-la-Neuve in the last
decade . An upper limit of 21 meV (90 C.L.) was set on the resonance strength of the 2.643 MeV level [3].
These investigations had two drawbacks, i.e. a low detection efficiency, of the order of 1.5 %, and the presence
of a background from the 19Ne(d,n)20Na competing reaction, induced by the beams on deuterium present in the
CH2 target. The latter imposed an additional measurement on a CD2 target to be made after each (p,γ)
measurement.
[2]
ARES, the Astrophysics REcoil Separator, was built to measure radioactive capture of astrophysical
interest by detecting the product ions. The inverse kinematics implies that product and beam ions have the same
momentum behind the target. A velocity selection with a Wien filter allows us to reject the beam ions. A charge
selection is realized before this Wien filter with a dipole magnet. A ∆E-E detector provides an additional
rejection. ARES has been intensively tested with a (p,γ) reaction induced by a stable beam: 19F(p,γ)20Ne (ER=
635 keV, ωγ=1.6 eV, Γ= 6.3 keV) [4]. The main results are the following: a transmission of 11.5 % was measured
for the 20Ne7+ product ions (the most abundant charge state); the charge distribution of 19F and of 20Ne ions
behind the CH2 target was measured and was found in good agreement with the Shima et al. [5] calculation; the
measured energy distribution of the product ions was fairly well reproduced by a GEANT simulation.
The study of the 19Ne(p,γ)20Na reaction should benefit from two improvement as compared with
previous methods: a slightly larger transmission efficiency (~ 4 %, from the product of the most abundant charge
state (7+) production efficiency beyond the target and the transmission of 20Na7+ in ARES) and suppression of the
background from (d,n) reaction. Simulations of the 19Ne(d,n) reaction in ARES showed indeed a null
transmission of 20Na7+ ions from this reaction.
3
1.2.1. Beam related measurements
The recoil proton spectra from 19Ne(p,p) elastic scattering has been fitted with a Rutherford cross
section, as the resonance width is smaller than the lower limit (~ 0.5 keV, see [6]) able to distort in a significant
way the classical Coulomb pattern. An average 19Ne3+ beam on target of (1.08 ± 0.11)108 pps has been obtained.
The beam purity has been measured by transporting a 19Ne beam with a reduced intensity through ARES. The
identification of the particles in the ∆E-E detector lead to a contamination in 19F of at most 0.7 %. A FWHM of
the beam energy distribution of 260 keV was measured in a pips detector at the target place.
1.2.2. Results
ARES was tuned as follows : The 19Ne7+ beam was transported through ARES, all the elements being
optimized successively. Typical transmission of 60 % was obtained. Then knowing the energy of 20Na ions
behind the target, the dipole field and the Wien filter magnetic field were changed accordingly to transport 20Na
ions to the ∆E-E detector. A rejection factor of the 19Ne beam of 5.10-6 has been calculated. This is roughly a
factor 10 worse than the one obtained in the 19F(p,γ)20Ne test reaction. The lower quality of the radioactive beam
is probably the reason far that.
The ∆E beam gas counter was operated at a pressure of 4 mbar isobutane. Figure 1 presents a twodimensional spectrum of the ∆E vs E+∆E events. The dark area is the region of the 19Ne ions. A solid line
surrounds the region of the 20Na ions, which was determined from a simalution of 20Na events tracked trough
ARES from the target to the ∆E-E detector. Two regions of equivalent surface were selected right and left to the
region of interest. Pile-up events, occurring in the regions at a level of 10-7 of the leaky beam events, were
summed and subtracted from the counts in R.O.I.
Figure 1 : Two-dimensional spectrum ∆E vs E+∆E, in the end detector of ARES for the
19
Ne(p,γ)20Na reaction. The dark area consists in 19Ne leaky beam events. The
leaky 19F contaminant beam events are visible just below the 19Ne region, in log
scale. The framed area limited by solid lines is the expected location for 20Na
events from 2.643 MeV level. Adjacent regions limited by dashed lines are used
to estimate the background.
The remaining counts were corrected for the efficiency of the set-up, which is the product of the amount
of 20Na7+ ions after the target (0.37, see [5]) and the transmission of 20Na7+ in ARES deduced from simulations.
The global efficiency was 2.7 %. The resonance strength ωγ is given by:
ωγ =
where
mt
Y 2
⋅ ⋅ ε lab ⋅
2
I λ
mt + mp
Y is the number of 20Na events corrected for the efficiency;
I is the integrated 19Ne beam intensity;
λ is the C.M. Wave length (in cm2);
εlab is the stopping power of the 19Ne ions CH2 (in 10-15 eV.cm2/at);
mp (mt) is the mass of the target (of the projectile) in AMU.
4
The final result is ωγ =-1.0 ± 9.6 meV. To the 9.6 meV statistical error a systematic error of 0.6 meV
has been added. The latter comprises the uncertainty to the integrated beam intensity and the transmission of
ARES. Both types of errors were combined in quadrature, the positive part of the Gaussian distribution of the
result was renormalized to 1, and an upper limit of 15.2 meV (90 % C.L.) was obtained. This value reduces
slightly the upper limit from our first experiment [3]. A detailed report on the present measurement has been
submitted for publication [7].
[1] M. Wiescher, J. Görres and H. Schatz, J. Phys. G25 (1999) R133.
[2] R.D. Page et al., Phys. Rev. Lett. 73 (1994) 3066.
[3] G. Vancraeynest et al., Phys. Rev C57 (1998) 2711.
[4] M. Couder et al., Nucl. Instr. Meth. Phys. Res. A506 (2003) 26.
[5] K. Shima et al., Atomic Data and Nucl. Data Tables 51 (1992) 173.
[6] R. Coszach et al., Phys. Rev. 50 (1994) 1695.
[7] M. Couder et al., Phys. Rev. C69 (2004) R022801.
1.3. The 18F(α,p)21Ne reaction: a key to understanding neutron production
in r-process sites
D. Groombridge, S. Fox, B. Fulton, D. Watson (Department of Physics, University of York, York, UK); M.
Wiescher, S. Dababneh, J. Görres, H. Lee, S. O’Brien (University of Notre Dame, Indiana, USA); C. Angulo, E.
Casarejos, M. Couder, P. Leleux (Centre de Recherches du Cyclotron et Institut de Physique Nucléaire,
Université catholique de Louvain, Louvain-la-Neuve, Belgium); M. Aliotta, A. Murphy (Department of Physics
and Astronomy, University of Edinburgh, UK); A. Laird (TRIUMF, Vancouver, Canada); D. Galaviz
(Technische Universität Darmstadt, Germany)
Résumé : Nous avons entrepris une mesure directe de la réaction 18F(α,p)21Ne entre 1.2 MeV et 2.0 MeV c.m.,
au moyen d’un faisceau de 18F radioactive. Cette mesure répondra à la question suivante : la suite
14
N(α,γ)18F(α,p)21Ne(α,n) produit-elle assez de neutrons pour expliquer la présence d’un processus-r
dans la couche riche en He d’une étoile au stade pré-supernova ?
Recent observations of the abundance distribution of heavy elements in metal poor old stars give a
strong indication on the existence of more than one r-process site [1]. These observations indicate that the heavy
r-process elements with A > 130-140 must have originated at a different site than the less massive ones with A <
130-140. This interpretation of the observed abundance pattern has rejuvenated many of the previously
proposed models for r-process sites which were originally deemed insufficient in providing a high enough
neutron flux for the production of the very heavy elements. Of particular interest is the model about r-process
nucleosynthesis in the supernova shock through the He-rich shell of the pre-supernova star [2]. In this scenario,
the neutrons are released by 18O(α,n) or 22Ne(α,n) reactions with 18O and 22Ne being produced by the reaction
sequence 14N(α,γ)18F(β+)18O. In view of the new observational data, reconsideration of the model suggested that
additional neutron production is necessary to obtain the anticipated r-process abundance distribution below
A=130-140 [3]. The 13C(α,n) reaction was considered as a possible neutron source, which would require a
considerable 13C abundance in the He-shell. An alternative neutron source, which had not been considered, is
provided with the rapid depletion of 14N in the shock through the reaction sequence 14N(α,γ)18F(α,p)21Ne(α,n).
The α capture on 18F will be considerable faster than the beta decay at the high densities and temperature
conditions in the shock. The reaction 21Ne(α,n) has a positive Q-value and has been identified as a strong
neutron source [4]. The total neutron production therefore depends mainly on the 14N abundance and on the
reaction rates of 14N(α,γ)18F and 18F(α,p)21Ne. The first reaction has been measured in great detail and the results
indicate a smaller reaction rate than previously anticipated [5]. The second reaction has not been measured until
now. Experimental studies of the inverse 21Ne(p,α)18F process, however, indicate that the cross section might
differ considerable from standard Hauser-Feshbach calculations, due to strong low energy resonances [6] .
The 18F(α,p)21Ne reaction was studied using a high efficiency detector/target geometry and a
radiative beam. Figure 1 shows some photographs of the experimental set-up at the CRC.
5
18
F
(a)
Figure 1 :
(b)
(c)
Photographs of the experimental set-up showing: (a) The He gas cell mounted in the vacuum chamber.
The Ni entrance window and the surface barrier detectors used for normalising the beam can be seen in
the upper picture and the segmented Ni exit window can be seen in the lower picture, (b) the CD and (c)
the LEDA detectors mounted in the chamber.
A gas cell (8 cm in length and 6 cm in diameter) was used together with a CD detector [7] and a LEDA
detector in a ∆E-E configuration. A 2 µm Ni foil, 12 mm in diameter, was used as the entrance window and a
6 µm Ni foil used for the segmented exit window, with a 12 mm diameter Ta foil at the centre to stop the beam.
The gas cell was filled with 250 mbar of He gas. The CD detector, placed at a distance of 11 cm from the
entrance window, consisted of four quadrants each with 16 annular strips and a thickness of 45 µm. The LEDA
detector, placed at a distance of 35 cm from the entrance window, consisted of 8 sectors each with 16 annular
strips and a thickness of 300 µm. This combination provided good particle identification and also an accurate
measurement of the scattering angle. The protons of interest are selected from the ∆E-E spectrum. Knowledge
of the position in the detectors where a proton hit allows its trajectory to be reconstructed to a position of origin
in the gas. This in turn gives information on the level structure in 22Na, since a position in the gas can be related
to the energy at which the reaction occurred through knowledge of the energy loss of the beam in the gas. The
experiment was successful and we achieved very good statistics (~ 1500 protons) in the allocated schedule.
Work on the analysis of the experimental data is still underway.
[8]
[1] C. Sneden, Nature 409, 673 (2001).
[2] J.W. Truran, J.J. Cowan, A.G.W. Cameron, Astrophys.J. 222, L63 (1978).
[3] J.W. Truran, J.J. Cowan, in Proceedings of the 10th workshop on Nuclear Astrophysics, Ringberg Castle,
eds. W. Hillebrandt, E. Müller, MPA/P12 (2000), p.64.
[4] A. Denker, H.W. Drotleff and M. Grosse et al. in Nuclei in the Cosmos III, AIP Conference Proceedings
327 (1994) 255.
[5] J. Görres, C. Arlandini, U. Giesen et al., Phys. Rev. C62 (2000) 055801-1.
[6] J. Görres, M. Wiescher, U. Giesen et al., Bul. Am. Phys. Soc. 33 (1988) 1563.
[7] A.N. Ostrowski et al., Nucl. Instr. Meth. Phys. Res. A480 (2002) 448.
[8] T. Davinson et al., Nucl. Instr. Meth. Phys. Res. A454 (2000) 350.
6
2. NOYAUX EXOTIQUES / EXOTIC NUCLEI
2.1. Study of the proton drip line nucleus
scattering
11
N by
10
C+p resonant elastic
C. Angulo, E. Casarejos, M. Gaelens, M. Loiselet, Th. Keutgen, P. Leleux, A. Ninane, G. Ryckewaert, F.
Vanderbist (Centre de Recherches du Cyclotron and Institut de Physique Nucléaire, Université catholiquede
Louvain, Louvain-la-Neuve, Belgium); M. Aliotta, T. Davinson, Z. Liu, A.S. Murphy, I.J.M. Roberts, P.J.
Woods (Department of Physics and Astronomy, University of Edinburgh, UK); J.S. Schweitzer (Laboratory for
Nuclear Science, University of Connecticut, Storrs, USA); P. Descouvemont, (Physique Nucléaire Théorique et
Physique Mathématique, ULB, Brussels, Belgium)
Résumé : Dans le but d’étudier le noyau riche en protons 11N, nous avons mesuré la section efficace élastique
10
C+p en cinématique inverse avec un faisceau radioactif de 10C. Nous avons utilisé le système de
détection ‘CD’ (∆E-E) pour détecter les protons de recul. Dans une analyse préliminaire utilisant la
méthode de la matrice R, nous avons obtenu l’état fondamental du 11N à une énergie Ec.m. ~ 1.45 MeV
au-dessus du seuil 10C+p avec une largeur proton Γp ~ 1 MeV. Ces résultats sont importants pour
comprendre la décroissance en deux protons du noyau 12O. Le mécanisme de décroissance en deux
protons est actuellement un des sujets les plus importants en physique nucléaire.
The structure and decay modes of light exotic nuclei are a major area of interest in nuclear physics
research. Proton-rich nuclei are particularly interesting since the level scheme is not known for many species.
The dedicated production and acceleration of intense low-energy radioactive beams allow at present
investigations of the properties of low-lying states in many proton drip-line nuclei. The experimental techniques
used for these investigations are diverse and their application often depends on the properties of the radioactive
beams (energy, intensity) and the characteristics of the experimental apparatus. Here we present preliminary
results obtained on the proton-rich nucleus 11N using the 10C +p resonant elastic scattering technique in inverse
kinematics [1].
The nucleus 11N, mirror nucleus of 11Be – the most famous case of shell inversion (between the 1/2+
ground state and the 1/2- first excited state) –, is proton unbound by about 1.3 MeV [2]. Understanding the lowenergy states in 11N is a significant test of nuclear models [3]. The energy and decay width of the 11N ground state
is also an important ingredient in predicting the two proton decay width of the ground state of 12O [4]. The
mechanism of the two proton decay is a major topic in nuclear physics [5]. Much effort has been devoted to
elucidating the low-energy resonance structure of 11N [6,7], but there remains considerable disagreement in the
most recent experimental results particularly with respect to the ground state.
A new dedicated study of the 11N ground state has been performed at the CRC, using the recently
developed 10C2+ beam at laboratory energies of 25.5 and 32 MeV (averaged intensity on target was about 3×104
pps). Due to the expected large width of the state, we used a 2 mg/cm2 thick polyethylene target. The recoil
protons were detected using a ∆E-E detector system [8]. Figure 1 shows a typical ∆E-E spectrum for a c.m. angle
θc.m. = 150°. The recoil proton signal is outlined in the figure.
Figure 1 : Typical ∆E–E spectrum from the
outlined.
10
C+p elastic scattering. The recoil protons are
7
From the recoil proton spectra we have obtained differential cross sections for c.m. angles θc.m. = 140° –
172° and c.m. energies Ec.m. = 0.7 – 2.8 MeV. Figure 2 shows preliminary results of the differential cross section
versus c.m. energies for two typical c.m. angles θc.m. = 143.6º and θc.m. = 169.8º. The errors in the figure are
statistical only. The dotted curve is the Rutherford cross section. The low energy 10C+p elastic cross section is
influenced by states located at higher energies. In a preliminary R-matrix [9,10] analysis of the data, including 3
resonant states (1/2+, 1/2- and 5/2+) in the c.m. energy range Ec.m. = 1 – 4 MeV, we obtain for the ground state of
11
N an energy Ec.m. ~ 1.45 MeV above the 10C+p threshold and a width Γp ~ 1 MeV (red curve in Figure 2).
These results are in fair agreement with previous results using the 10C+p system[6], but in clear disagreement with
the more recent results of Guimarães et al. [7] that obtained a width Γp =0.24 ± 0.24 MeV, using the transfer
reaction 14N(3He,6He)11N and a DWBA analysis (blue curve in Figure 2).
Figure 2 : Preliminary results of the 10C+p elastic cross section versus c.m. energies for c.m. angles 169.8º and
143.6º (solid points). The red solid curves are the best R-matrix fit (χ2/N=0.9; N=223; a=6 fm). The blue
solid curves are the R-matrix calculations using the parameters of Ref. [7] (for a=6 fm). The dotted curves
are the Rutherford cross sections.
A detailed R-matrix analysis of the data is presently underway and a publication is in preparation.
This work has been supported by the European Community-Access to Research Infrastructure action of
the Improving Human Potential Program, contract Nº HPRI–CT–1999–00110 and the PAI program P5/7 on
Interuniversity Attraction Poles of the Belgian-state Federal Services for Scientific, Technical and Cultural
Affairs.
[1] C. Angulo, Nucl. Phys. A., in press (Proc. Int. Conf. on Radioactive Nuclear Beams 6, Sep. 21 – 27, 2003,
Argonne, USA).
[2] TUNL Nuclear Data Evaluation, http://www.tunl.duke.edu/nucldata/update/11/11n.shtml
[3] H.T. Fortune, Phys. Rev C51 (1995) 3023; F.C. Barker, Phys. Rev. C53 (1996) 1449; P. Descouvement,
Nucl. Phys. A615 (1997) 261; S. Grévy et al., Phys. Rev. C56 (1997) 2885.
[4] R.A. Kryger et al., Phys. Rev. Lett. 74 (1995) 860.
[5] P.J. Woods, Science 291 (2001) 995.
[6] K. Markenroth et al., Phys. Rev. C62 (2000) 034308 and references therein.
[7] V. Guimaraẽs et al., Phys. Rev. C67 (2003) 064601.
[8] A.N. Ostrowski et al., Nucl. Inst. Meth. Phys. Res. A480 (2002) 448.
[9] A.M. Lane and R.G. Thomas, Rev. Mod. Phys. 30 (1958) 257.
[10] C. Angulo and P. Descouvemont, Phys. Rev. C61 (2000) 06461.
8
2.2. Spectroscopy of 7He by the 9Be(6He,7He)8Be transfer reaction
E. Casarejos, C. Angulo, J. Cabrera, Th. Keutgen, A. Ninane (Centre de Recherches du Cyclotron and Institut de
Physique Nucléaire, UCL, Louvain-la-Neuve, Belgium); R. Raabe, J.L. Charvet, A. Gillibert, V. Lapoux, L.
Nalpas, A. Obertelli, F. Skaza, J.L. Sida (DAPNIA/SPhN, CEA Saclay, France); N. Orr (LPC Caen, France); S.
Sidarchuk, R.Wolski (FLNR, Dubna, Russia), D. Smirnov (Instituut voor Kern-en Stralingsfysica, KULeuven,
Belgium), D. Escrig (Instituto de Estructura de la Materia, CSIC, Madrid, Spain), A. Moro (Departamento de
Física, Instituto Superior Técnico, Oeiras, Portugal)
Résumé : L’état fondamental du 7He (J=3/2-), observé dans plusieurs expériences, est instable vers 6He + n
avec un seuil de -0.44 MeV. Des états excités 1/2− et 5/2− sont prédits par des modèles théoriques,
mais les résultats expérimentaux sont peu concluants. Nous avons étudié le 7He avec la réaction de
transfert 9Be(6He,8Be)7He utilisant un faisceau radioactif de 6He à 17 MeV et une cible de 9Be. Les
particules α provenant du break-up du 8Be on été détectés avec le système LEDA. Des résultats
préliminaires sont présentés.
The ground state of the neutron rich nucleus 7He is unstable by 0.44 MeV with respect to the decay into
He + n . It has been observed in several experiments, the first one 35 years ago [2]. Until recently, however, no
evidence was found for excited states at energies up to at least 10 MeV. A number of calculations have been
published on 7He in the last decade [3-6]. While the results differ in some aspects (like the presence of other
excited states at higher energies), they all agree in predicting at least two resonances, 1/2− and 5/2−, above the
3/2− ground state. Only in the last few years the advent of radioactive ion beams has opened new experimental
possibilities, renewing interest in the study of this isotope. For the first time, two resonances corresponding to
excited states were observed in various experiments [7-10]. However, uncertainties are present in the spin
assignment of these resonances, because they were not observed together in any of the experiments performed so
far.
6
[1]
The experiment performed at the CRC-UCL aimed at investigating the 7He nucleus using the reaction
Be( He, Be)7He. The detection of the two α particles resulting from the break-up of 8Be is a clear signature of
the reaction channel, and the 7He spectrum can be reconstructed by the missing-mass method. In addition, the
measurement of the angular distribution allows determining the spin of the possible states.
9
6
8
Prior to the study of 7He, and in order to test the proposed experimental method, the reaction
Be( Li, Be)7Li was used to investigate the 7Li nucleus. The spectrum obtained in this measurement in shown in
Figure 1. The energy levels of 7Li are reproduced with excellent precision and resolution, showing the suitability
of the method to study 7He.
9
6
8
Figure 1 : Q-value spectrum of the 9Be(6Li, 8Be)7Li events.
In a second step, the reaction 9Be(6He,8Be)7He was studied using a 17 MeV 6He beam and a 9Be selfsupporting target. The α particles from 8Be were detected by the LEDA silicon strip array system [11] covering
laboratory angles from 5° to 12°. The unambiguous identification of α particles was performed in a Time-Of9
Flight versus E spectrum. The coincidence of two α particles in one event was used as signature to reconstruct
the 7He level scheme. Preliminary results are show in Figure 2. The observed energy of the ground state is in
agreement with previous results and the good statistics will allow extracting the angular distribution and,
therefore, establishing the spin of this state. The spectrum shows no other narrow state. The analysis of the
different components that should contribute to the missing-mass spectrum will finally determine if any other
state is present in our data. Such detailed analysis of the data is underway and a publication is in preparation.
Figure 2 : Preliminary Q-value spectrum of the 9Be(6He, 8Be)7He events.
Affairs.
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
See e.g. the compilation by the TUNL Nuclear Data Evaluation, http://www.tunl.duke.edu.
R.H. Stokes and P.G. Young, Phys. Rev. Lett. 18 (1967) 611; Phys. Rev. 178 (1969) 2024.
N.A.F.M. Poppelier, A.A. Wolters, P.W.M. Glaudemans, Z. Phys. A346 (1993) 2024.
J.Wurzer, H.M.Hofmann, Phys. Rev. C55 (1997) 688.
B.S. Pudliner, V.R. Pandharipande, J. Carlson, S.C. Pieper, R.B. Wiringa, Phys. Rev. C56 (1997) 1720.
K. Arai, P. Descouvemont, D. Baye, Phys. Rev. C63 (2001) 44611.
A.A. Korsheninnikov et al., Phys. Rev Lett. 82 (1999) 3581.
H.G. Bohlen et al., Prog. Part. Nuc. Phys. 42 (1999) 47; H.G. Bohlen et al., Phys. Rev. C64 (2001) 024312.
M. Meister et al., Phys. Rev. Lett. 88 (2002) 102501; K. Markenroth et al., Nucl. Phys. A679 (2001) 462.
M.S. Golovkov et al., Phys. At. Nuc. 64 (2001) 1244.
T. Davinson et al., Nucl. Instr. Meth. Phys. Res. A454 (2000) 350.
2.3. Spectroscopy of 5H by the 7Li(6He,5H)8Be transfer reaction
E. Casarejos, C. Angulo, P. Demaret, Th. Keutgen, A. Ninane (Centre de Recherches du Cyclotron and Institut
de Physique Nucléaire, UCL, Louvain-la-Neuve, Belgium); R. Raabe, J. Ponsaers (Instituut voor Kern-en
Stralingsfysica, Katholieke Universiteit Leuven, Leuven, Belgium); M. Aliotta, T. Davinson, C. Ghag, Z. Liu,
A.S. Murphy (Department of Physics and Astronomy, University of Edinburgh, UK); N.L. Achoury, N. Orr
(LPC Caen, France); S. Sidarchuk, R.Wolski (FLNR, Dubna, Russia); J.S. Schweitzer (Laboratory for Nuclear
Science, University of Connecticut, Storrs, USA); A. Di Pietro (LNS and INFN Catania, Italy); P.
Descouvemont (Physique Nucléaire Théorique et Physique Mathématique CP-229, ULB, Brussels, Belgium)
Résumé : Le noyau 5H, riche en neutrons et instable en particules, est caractérisé par un rapport N/Z parmi les
plus élevés connus (N/Z=4). L’étude de ce noyau est donc importante pour une meilleure
connaissance des propriétés nucléaires dans des conditions extrêmes. Des expériences antérieures
observent l’état fondamental à environ 2 MeV au dessus du seuil t + n + n. La largeur de l’état
fondamental, ainsi que l’existence d’états excités prédits par la théorie, restent largement incertains,
et nécessitent de nouvelles approches expérimentales. Nous avons étudié le 5H avec la réaction de
transfert 7Li(6He,8Be)5H utilisant un faisceau radioactif de 6He à 30 MeV et une cible de 7Li.
10
The study of nuclei beyond the drip lines is expected to provide a stringent test for nuclear structure
models. The search for heavy H isotopes started more than 30 years ago. In spite of the considerable
experimental efforts [1-4], the structure of the neutron rich nucleus 5H, characterized by an N/Z ratio among the
largest known (N/Z=4), remains poorly known. The models that describe the resonant states of the unstable 5H
predict broad states at low energies, being the ground state located at about 3 MeV above the t+n+n threshold [69]
. The use of radioactive ion beams has shown clear advantages in recent years, opening new experimental
possibilities.
The experiment performed at the CRC-UCL aimed at investigating the low-energy level scheme of the
H nucleus using the 7Li(6He,8Be)5H transfer reaction. The detection of the two α particles resulting from the
decay of 8Be is a clear signature of the reaction channel allowing reconstructing the 5H spectrum by the invariant
mass method. In addition, the measurement of the angular distribution will allow determining the spin of the
states. The method has been demonstrated suitable by previous investigations (see, for example, report on 7He).
The success of the experiment relies also in the quality of the 7Li target, whose oxygen content determines the
final resolution of 5H state candidates. Such target has been successfully produced at the UCL.
5
The experiment was performed with a 30 MeV 6He beam and the α particles were detected by two
LEDA silicon strip arrays[10] covering laboratory angles from 3° to 23°. The unambiguous identification of the α
particles is performed by a selection in a Time-Of-Flight (TOF) versus E spectrum (see Figure 1). The
coincidence of two α particles in one event is used as signature to reconstruct the 5H spectrum.
Figure 1 : TOF versus energy spectrum (in relative units) from 7Li(6He, 8Be)5H for a typical
angle. The α particles from the decay of 8Be are marked by a selection.
The analysis of the different components that should contribute to the invariant mass spectrum will
finally determine if any state is present in our data. Such detailed analysis of the data is presently underway.
Affairs.
[1] D.V. Aleksandrov et al., Proc. Int. Conf. Exotic Nuclei and Atomic Masses, ENAM'95, Arles, France,
1995.
[2] A.A. Kosheninninkov et al., Phys. Rev. Lett. 87 (2001) 0922501.
[3] M. Meister et al., Nuc. Phys. A723 (2003) 13; Phys. Rev. Lett. 91 (2003) 162504.
[4] M.S. Golovkov, Phys. Lett. B566 (2003) 70.
[5] J. Bevelacqua et al., Nuc. Phys. A357 (1981) 126.
[6] N. Poppelier et al., Phys. Lett. B157 (1985) 120.
[7] N.B. Shulgina et al., Phys. Rev. C62 (2000) 014312.
[8] P. Descouvemont et al., Phys. Rev. C63 (2001) 027001.
[9] M.G. Gornov et al., Nuc. Phys. A531 (1991) 613.
[10] T. Davinson et al., Nucl. Instrum. Meth. Phys. Res. A454 (2000) 350.
11
2.4. Sub-barrier fusion study of light nuclei : 7Be + 238U
R. Raabe, J.-L. Charvet, C. Jouanne, L. Nalpas, J.-L. Sida (SPhN, CEA Saclay); C. Angulo (CRC, Louvain-laNeuve); P. Figuera (LNS Catania); D. Pierroutsakou, M. Romoli (INFN Napoli); J.-M. Casandjian (GANIL,
Caen)
Résumé : Les réactions 7,9Be, 7Li + 238U ont été mesurée aux énergies autour des leurs barrières coulombiennes
respectives. Le système de détection nous a permis de distinguer entre les contributions dues à la
fusion et celles dues au processus de transfert/break-up. Une analyse comparative des trois systèmes
peut aider à évaluer le rôle du couplage avec les canaux du transfert et break-up dans le mécanisme
de réaction de fusion.
Quantum tunnelling is extremely sensitive to the presence of many degrees of freedom [1]. In nuclear
physics, this appears as a dependence of the fusion cross section around the barrier upon the coupling to other
reaction channels, such as inelastic scattering, transfer and break-up [2]. In light nuclei these channels may be of
particular importance, as these systems often present pronounced clustering, extended matter distributions and
low break-up thresholds.
Using the radioactive beams available at the CRC in Louvain-la-Neuve it was possible to continue the
research on this topic, already started with the study of reactions with the halo-nucleus 6He [3]. In the new
experiment we studied the reactions induced by beams of 7Be, 9Be and 7Li nuclei on a 238U target, around the
respective barrier energies. The beam nuclei impinged on a thin (500 µg/cm2) UF4 target deposited on a C foil.
Fusion reactions led to the fission of the compound nucleus, identified by the coincident detection of the two
fragments in an array of silicon detectors surrounding the target. Contribution to the fission cross section, due to
transfer and break-up reactions (collectively denoted here as quasi-elastic), was discriminated by the coincident
detection of a third charged particle. Information on the angular distribution of the latter processes is necessary
in order to extract the actual efficiency of detection and correctly perform the subtraction from the total fission
cross section.
Results for the fission cross sections and preliminary results for the fusion and quasi-elastic cross sections
are presented in Figure 1. The fusion cross section for 7Be + 238U, measured at energies well below the barrier,
does not show an increase with respect to calculations using a one-dimensional barrier penetration model. At
energies above the barrier the fusion cross section is lower than the prediction. The quasi-elastic contribution
becomes dominant at the lower energies. A coupled-channel analysis, including couplings to transfer and
continuum channel, is being performed in order to achieve a coherent description of all measured quantities.
Figure 1 : Left: measured fission cross sections for the systems 7,9Be,7Li + 238U. For 7Li + 238U data from
literature are also included. Right: Fusion (filled symbols) and quasi-elastic (hollow symbols) cross
sections for the same systems, plotted as function of the ratio between the centre-of-mass energy and
the potential barrier. The curves are predictions for the fusion cross sections according to a onedimensional barrier penetration model.
[1] M. Tsukada et al. (eds.), Proceeding of the Fourth International Symposium on Foundations of Quantum
Mechanics, Tokyo 1993, Japanese Journal of Applied Physics Series 9.
[2] R. A. Broglia et al., Phys. Rev. C 27 (1983) 2433; C. H. Dasso, S. Landowne, and A. Winther, Nucl. Phys.
A407 (1983) 221.
[3] M. Trotta et al., Phys. Rev. Lett. 84 (2000) 2342; J. L. Sida et al., Nucl. Phys. A685 (2001) 51c.
12
2.5. Measurement of the 6He β−delayed α+d emission branching ratio
D. Smirnov, F. Aksouh, S. Dean, H. De Witte, J. Gentens, I. Mukha, M. Huyse, O. Ivanov, P. Mayet, R. Raabe,
P. Van den Bergh, K. Van de Vel, J. Van de Walle, P. Van Duppen (IKS, KU Leuven); C. Angulo, J. Cabrera, A.
Ninane, P. Demaret (Centre de Recherches du Cyclotron et Institut de Physique Nucléaire, Université catholique
de Louvain, Louvain la Neuve, Belgium); T. Davinson (Univ. of Edinburgh)
Résumé : Nous avons mesuré la décroissance 6He → 6Li*→ α + d + e- + ν- (Q = 2.033 MeV) et la distribution
d’énergie α + d. Ce mode de décroissance, très faible (de l’ordre de 10-3-10-4 %) récemment
découvert, est comparé au mode de décroissance le plus important vers l’état fondamental du 6Li.
Nous avons implanté un faisceau de 6He à 7.5 MeV et un faisceau de 18Ne à 10 MeV dans un détecteur
(DSSD) avec des pixels de petites dimensions pour réduire la sensibilité aux particules β de l’6He et
du 18Ne. Des résultats préliminaires sont présentés.
After the pioneering measurement [1] of the α+d delayed emission in 1990 where the branching ratio
was determined for the first time, two other measurements [2,3] were performed showing an obvious discrepancy.
The present data available vary within a factor 3 (Table 1). Besides the experimental aspect, the calculation of
the α+d channel transition probability [4-9] shows that the neutron halo part of 6He plays an important role in the
quenching of this channel and thus offers a sensitive test to its halo structure. Except the result in [6] which is
consistent with the value measured in [3], the theoretical determinations are presently much larger than
experiment.
Reference
Branching ratio (10-6)
Cutoff energy
Ed > E0
E0 (lab), keV
2.8 (5)
7.6 (6) (a)
1.8 (9)
2.6 (1.3)
200
30-40
3.1
250
350
350
0
250
[1] Isolde (1990)
[2] Isolde (1993)
[3] Triumf (2002)
[4] Two center cluster model
[5] Three-body (α,n,n) model
[6] Dynamical Microscopic Cluster Model
350
Table 1 : Present experimental data and theoretical calculations available on the 6He → 6Li* → α + d
+e-+ν- branching ratio.
(a) Recommended by the authors of [2] as compared to their previous value in [1] which was
discarded.
In order to reduce the β−background originating from the main decay branch and to obtain an absolute
normalization, an 7.5 MeV radioactive 6He beam was implanted in a highly pixelated (DSSSD type) Si detector
with an active area 16 mm x 16 mm at a rate of ~ 5⋅103 ions per second. The wafer thickness being 78 µm, this
energy was chosen in order to stop the ions at the middle of the detector. The front face consists of 48 p+n strips
while the back face has 48 n+n ohmic strips perpendicular to the first ones, thus forming an ensemble of ~ 2300
pixels. The strip pitch is then 335 µm while the strip width is 300 µm. The small volume of the pixels ensured
the low sensitivity to β−particles while the normalization was obtained by measuring the number of implanted
6
He nuclei: from the simulations, the α’s and deuterons deposit all their energy into only 1 pixel while the β’s
into more pixels. In other words, below the cutoff energy, the probability to detect one direct β−decay event in
one pixel becomes comparable as compared to the detection of an (α+d) event. The sensitivity to β−particles was
checked by implanting a 10 MeV post-accelerated 18Ne beam whose β+ spectrum has roughly the same end-point
energy (Q = 3.424 MeV) compared to the β− spectrum of 6He (Q = 3.508 MeV).
The average energy resolution was 22 and 27 keV for the p+n and n+n strips respectively using the
5805 keV α line of 244Cm. The beam distribution in space as well as in time was a key point. The beam had to be
uniformly distributed on the detector surface in order to avoid a too large counting rate per strip. In reality, the
beam was relatively concentrated on one edge of the detector (Figure 1) and as a result, the corresponding p+n
channels generated much more noise than the rest of the detector that was ‘normally’ illuminated. This effect
was taken into account and our data were corrected accordingly. Concerning the time structure, we were
alternating irradiation periods of 1 s (beam ON) and 2 s decay periods (beam OFF). The beam suppression factor
13
between the two time intervals was only about 3300 instead of an ideal value of 106-108 due to beam leaks in the
OFF period.
Figure 1 : Beam distribution over the detector showing the number of counts where one hit was registered in a front strip
and a back strip (left 6He and right 18Ne).
The total corrected number of implanted ions was 1.86 x 109 (6He) and 1.31 x 109 (18Ne) while the
number of recorded decays was 91250 (6He) and 50130 (18Ne). The number of 6He decays into the
α + d branch was determined from an accurate comparison between the decay spectra of the two nuclei. The
intermediate analysis of our data enables us to deduce a branching ratio B ≈ 10-6 which was determined for Ed,cms
> 525 keV (350 keV lab) and as is shown in Figure 2 agrees with recent data of D. Anthony et al.[3]. The data
analysis is being finalized in order to get the uncertainties and the results will be published soon.
Figure 2 : Energy distribution of the (α + d) decay transition probability from the present
work (LLN) compared to the two previous measurements from Isolde.
[1] K. Riisager et al., Phys. Lett. B235 (1990) 30.
[2] M. J. G. Borge et al., Nucl. Phys. A560 (1993) 664.
[3] D. Anthony et al. Phys., Rev. C65 (2002) 034310.
[4] P. Descouvement and C. Leclercq-Willain, J. Phys. G 18 (1992) L99.
[5] M. V. Zhukov et al., Phys. Rev. C47 (1993) 2937.
[6] A. Csoto and D. Baye, Phys. Rev. C49 (1994) 818.
[7] D.Baye, Y.Suzuki, P.Descouvemont, Prog. Theor. Phys. 91 (1994) 271.
[8] F.C.Barker, Phys. Lett. B322 (1994) 17.
[9] K.Varga, Y.Suzuki, Y.Ohbayasi, Phys. Rev. C50 (1994) 189.
14
3. RÉACTIONS ET STRUCTURES NUCLÉAIRES / REACTIONS AND NUCLEAR
STRUCTURES
3.1. Properties of neutron emission in fission processes induced by
20
Ne+159Tb and 20Ne+169Tm reactions between E = 8 and 16 MeV/
nucleon
Th. Keutgen, J. Cabrera, Y. El Masri, Ch. Dufauquez, V. Roberfroid, I. Tilquin, J. Van Mol (FNRS and Institut
de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium); R. Régimbart
(Laboratoire de Physique Corpusculaire de Caen, France); R. J. Charity (Washington University, USA) ; J. B.
Natowitz, K. Hagel, R. Wada (Texas A&M University, USA) and D. J. Hinde (The Australian National
University, Australia)
Résumé : Ce travail concerne l’étude de l’émission neutronique lors de la fission induite dans les réaction
20
Ne+159Tb et 20Ne+169Tm à 8, 10, 13 et 16 MeV/nucléon. La configuration 4π du multidétecteur
DEMON a permis une investigation détaillée des propriétés des neutrons de pré- et de post-scission
en fonction des paramètres associés aux fragments de fission. Cette étude met clairement en évidence
l’isotropie de l’émission neutronique dans le repère de leurs sources émettrices. Par contre, la
détermination de la largeur de la distribution de la vitesse de recul du noyau composé et de l’énergie
cinétique totale dans le centre de masse des deux fragments de fission est biaisée par le recul subit
lors de l‘évaporation des particules légères de pré- et post-scission. Ce qui implique que toute
sélection réalisée sur ces deux quantités conduit à l’observation de distributions angulaires
anisotropes des particules légères émises. Les techniques d’ajustement de ces distributions pour
l’obtention des propriétés des particules de pré- et de post-scission ne peuvent plus être appliquées
dans de telles conditions.
3.1.1. Introduction
Neutron emission in E = 8, 10, 13 and 16 MeV/nucleon 20Ne +159Tb, 169Tm induced fission reactions
has been further studied. The 4π-configuration of the DEMON neutron multidetector allowed a detailed
investigation of the pre and postscission neutron properties as functions of the fission parameters.
The emission of the neutrons from their respective sources was found to be isotropic to a high degree.
The determination of the compound-nucleus recoil velocity (VCN) and the center-of-mass total kinetic-energy
(TKE) release in fission suffers from smearing due to the recoil kicks imparted by the evaporated pre and
postscission light particles. Attempts to gate on these quantities lead to biases in the emission patterns of the
evaporated neutrons. Specifically, with such gates, the assumption of isotropic emission is violated and attempts
to analyze such gated neutron spectra with the standard fitting technique, which assumes isotropy, lead to
spurious results. These effects are clearly illustrated in this work.
The study of neutron emission accompanying statistical fission has highlighted the important role of
dynamics and dissipation in fission-evaporation competition. Recently we have reported on the neutron and light
charged particles emitted in the E = 8, 10, 13 and 16 MeV/nucleon 20Ne +159Tb, 169Tm induced fission
reactions[1]. At the lowest bombarding energy, the fission process is entirely statistical and associated with
complete fusion. At the higher bombarding energies, the fission yield has increasing contributions from the fastfission process and the fraction of the projectile's linear momentum transferred to the fused systems decreases.
Due to their neutral charge, neutrons are not sensitive to the Coulomb field and thus, typically display
much higher multiplicities than the competing light charged particles in the decay of highly excited and rotating
nuclei. In the study of fission dynamics, neutrons, detected in coincidence with fission fragments (FF), are
assumed to originate from up to four moving sources. In temporal order, the first emitted are the preequilibrium
neutrons (PE) with multiplicity (νnPE), second are the prescission neutrons evaporated from the compound
nucleus (CN) prior to scission (νnCN), and last are the postscission neutrons evaporated from the two fission
fragment sources (νnF1 and νnF2). In our experiments, the PE neutron contribution was proportionately very weak
as compared to the contributions of the other neutron sources. However, the properties of this contribution have
made the object of a very detailed discussion in Ref. [1]. Therefore, in the following, we will concentrate the
discussion on the properties of the neutrons emitted by the three other sources.
15
3.1.2. Details on the experimental set-up and procedures of the data analysis
The experimental setup has been detailed in Ref. [1] and [2]. The neutron kinetic-energy spectra were
constructed from measured neutron times of flight and corrected for the energy-dependent intrinsic neutron
detection efficiency [3] . The spectra were normalized to their solid angles and the number of triggering FFs [4].
All double-differential multiplicity spectra d2νn/dΩ dEn from each DEMON detector were fitted by a single
theoretical function[2]. This function consists of the sum of four components; each associated with a particular
neutron source that emits isotropically in its rest frame. The sources are the preequilibrium neutron source PE,
the CN and the two fission fragments F1 and F2. The emission spectrum from the CN was assumed to be a
“surface” type Maxwellian distribution [1] .While the spectra associated with the FFs and the PE were assumed to
be a ”volume” type, or a Watt distribution [1].
In the fitting function, the parameters are :
CN
• Tn and νnCN the effective temperature of the CN source (assumed to recoil along the beam axis) and the
associated neutron multiplicity (prescission parameters);
• TnF1 and νnF1 the effective temperature of the F1 fission fragment detected in the MWPC 1 and the associated
neutron multiplicity (postscission parameters);
• TnF2 and νnF2 the effective temperature of the F2 fission fragment detected in the MWPC 2 and the associated
neutron multiplicity (postscission parameters);
• TnPE and νnPE "the effective temperature parameter" of the PE source and the associated neutron multiplicity.
These parameters were initially determined by fitting the double-differential neutron multiplicity spectra
d2νn/dΩ dEn for the whole set of DEMON detectors. Subsequently, in a second fit step, the effective
temperatures were held fixed and the multiplicity values were refined by fitting the neutron angular distributions
dνn/dΩ in and out of the reaction plane [1]. The data are generally well described by these four moving sources
with the assumption of an isotropic neutron emission in the rest frame of the emitting nuclei.
3.1.3. Neutron multiplicity distributions as a function of fission-fragment mass partition
Figure 1 shows the fitted neutron multiplicities and the effective nuclear temperatures as a function of
the fission-fragment mass AF1. The results are shown for both targets (Tm and Tb) at the four 20Ne beam
energies. The solid data points (triangles and circles symbols correspond to the Tb and Tm targets, respectively)
are associated with the fitted prescission neutron results νnCN, while the open data points are associated with νnFi.
The experimentally extracted prescission neutron multiplicity shows no significant AF1 dependence, while the
postscission multiplicities increase almost linearly with AF1. The effective temperatures also do not show any
significant dependence on the FF mass partition. The linear dependence of the postscission multiplicities is
consistent with a mass-partition-independent effective temperature for the postscission emissions.
16
Figure 1.
Figure 2.
Figure 2 shows the evolutions of the total neutron multiplicities νntot = νnCN + νnF1 + νnF2, as well as νnpost
= νn + νnF2, as a function of the FF mass partition. These total multiplicities are again independent of the FF
mass within the small experimental uncertainties. The total neutron multiplicity is related to the excitation
energy available for evaporation [5], which is the total excitation energy minus the Q value for fission (Qf) and the
corresponding TKE.
F1
Finally, while the mean (over FF masses) prescission neutron multiplicities increase almost linearly
(from 4.2 to 8.3) with CN excitation energy (from 108 to 254 MeV) independently of the FF mass partition, the
νnpost appears to saturate around a mean value of 4.2 (mean value over the FF masses and for the different
bombarding energies) starting already at ~100 MeV excitation energy (see also [1]). This saturation may even
start at lower E* [6]. This confirms that nuclear fission is a cold process occurring at very low excitation energy
and independent of the initial excitation energy of the fissioning nuclei at least above a given threshold (< 100
MeV).
17
3.1.4. Effets of the CN recoil velocity on the neutron angular distribution
3.1.4.1. CN recoil velocity distribution
In many previous studies, the contributions of the incomplete fusion (IF) process to the detected fission
events were accounted for by performing specific selections (cuts) on the CN recoil-velocity distributions. In fact
IF is normally characterized by an incomplete transfer of the projectile's linear momentum to the CN.
Consequently, the CN recoil velocity is expected to be lower than that for complete fusion, in which there is full
momentum transfer. In this work, the E = 10, 13, and 16 MeV/nucleon reactions show mean CN velocities
smaller than the expected complete fusion value and thus this indicates IF reactions are present[1]. For reactions
like these and others for which both complete and IF reactions may be mixed, if one wants to experimentally
reject the data events associated with incomplete fusion, a selection on the highest CN recoil velocities might
well be thought to be sufficient. We will show in this section and the following, that such selections on the recoil
velocity should be applied with a very great care.
as :
VCN distribution can be extracted from the measured FF velocities (VFi) and their detection angles (θi)
VCN =
VF1 VF2 sin (θ1 + θ2 )
VF1 sin (θ1 ) + VF2 sin (θ 2 )
This distribution for the E = 8 MeV/nucleon 20Ne+169Tm reaction is shown in Fig. 3 where bin cuts,
with comparable data statistics, are made on the VCN distribution. These cuts are numbered from 1 to 6 in Fig. 3.
For each cut, dνn/dΩ (θn) were determined. They are displayed by the solid circles in Figure 4 for the detectors
set in the reaction plane (φn = 0° and φn = 180°).
Figure 3.
For bin 4, the closest value to the mean recoil velocity of the CN in Fig. 3, the energy and angular
distributions were fitted in the manner discussed in previous Sect. 3.1.2 and displayed in Fig. 4. The dashed
curve represents the fit for the prescission neutron contribution, the dotted and dotted-dashed ones are those
associated with the FFs, and the solid curve is the sum of these three contributions (no PE contribution at 8
MeV/nucleon). This last curve is to be compared with the experimental data (solid circles). We observe an
excellent agreement. For the other bins, this total contribution curve is also shown and again should be compared
to the corresponding experimental points. Although at E = 8 MeV/nucleon no IF is contributing to the data[1], we
clearly observe in Fig. 4 an apparent dependence of the angular distribution on the VCN. This behavior is due to
the fact that the width of the recoil-velocity distributions is affected by the recoil effects associated with
evaporating these neutrons. Any constraint on the recoil velocity must bias the distribution of these coincident
neutrons.
18
Figure 4.
In bin 6, to obtain the highest VCN velocities, neutrons must be emitted at backward angles (|θn| > 90°).
Compared to the solid curve for which VCN is near its average value, the data in Fig. 4 (bin 6) show a strong
enhancement for |θn| > 90°. In contrast, the lowest VCN velocities will boost the forward emissions as shown in
Fig. 4 (bin 1). These observations lead to the conclusion that any cut on the VCN distribution affects the observed
isotropy, in their source frame, of the neutron emissions. Therefore the analysis method described in Sect. 3.1.2.
and [1], which assumes this isotropy as a fundamental hypothesis, is not anymore appropriate. Consequently, it is
clear that selecting the highest CN recoil velocities to isolate the complete-fusion events in a given nuclear
reaction, without taking into account the boost effects from the neutron emission, can lead to incorrect
determination of the fitted neutron emission properties.
Figure 5.
19
3.1.4.2. Effects of the FF mass and TKE distributions on the fission neutron multiplicities
Let us consider now selections on either the FF mass distribution or the TKE distribution choosing
again the data obtained with the E = 8 MeV/nucleon 20Ne+169Tm reaction. Fig. 5 shows how different cuts
operated on the FF mass partition (left), and on TKE (right), modify the corresponding VCN distributions.
Clearly, from Fig. 5b, the CN recoil-velocity distributions are not affected by any FF mass selection. In fact,
these distributions remain centered around the same VCN maximum with approximately equal widths.
As gating on TKE (horizontal cuts in Fig 5c) results in different AF1 distributions for each gate, Hinde et
al. [7] suggested gating on the related variable :
RTKE =
TKEexp
3
1/ 3
0.755 Z1 Z2 / ( A1/
1 + A 2 ) + 7.3
in order to ensure the AF1 distributions are approximately the same for each gate. The denominator of this
relation is the semi-empirical expression of Viola [8]extended by Hinde et al.[9] to account for asymmetric mass
partitions. Thus, RTKE = 1 (corresponding to the dashed curve in Fig 5c) represents the exact value of the Viola
systematic. Using constant RTKE cuts, as shown in Fig. 5c (bin cuts 1 to 5), we build the corresponding VCN
distributions plotted in Fig 5d. Clearly, such selections on RTKE induce different VCN distributions (labeled 1 to
5 in Fig. 5d) with different centroids and widths. In fact, one observes that the VCN centroids move to higher
values with increasing RTKE (from 0.7 to 1.15). As the CN recoil velocity is expected to be single valued, this
dependence on RTKE is an artifact of the analysis and again must be related to a bias in the neutron emissions.
Consequently if analyzed with the assumption of isotropic emission, it must clearly generate (as discussed
earlier) incorrect determinations of the neutron emission properties. Indeed, Fig. 6 shows the results of the fitted
neutron multiplicities as a function of RTKE for the reaction E = 8 MeV/nucleon 20Ne+169Tm. Obviously, we
observe a nonphysical increase in the prescission multiplicities νnCN with increasing the RTKE values. This
behavior is subsequently compensated by the decrease of the fitted νnF1 and νnF2 values.
Figure 6.
3.1.5. Conclusion
Neutron emission in the E = 8, 10, 13 and 16 MeV/nucleon 20Ne + 159Tb and 20Ne + 169Tm induced
fission reactions have been studied in great details. The properties of the neutron emission in and out of the
reaction plane have been established as functions of the fission mass partition, the center-of-mass total kineticenergy release in fission TKE, and the recoil velocity VCN of the compound nucleus. The isotropy of the neutron
evaporation in the rest frame of the emitting nucleus was clearly demonstrated. Within the small experimental
uncertainties, the extracted prescission neutron multiplicity was found to be independent of the fission fragment
mass partition. The extracted postscission neutron multiplicities were found to increase roughly linearly with
fragment mass as expected if the FFs, in all mass partitions, have a common T value.
The determination of the compound-nucleus recoil velocity, the kinetic-energy release in fission and the
fission mass partition suffer from a smearing due to the recoil kicks imparted by the evaporated pre and
postscission light particles. Any selection gating on the reconstructed quantities can impart a bias in the emission
pattern of these evaporated particles. Such effects were observed for the recoil velocity and the kinetic-energy
release in fission as the emission of the evaporated particles displays an apparent anisotropy in their source
frame. Analysis of such gated neutron data with the standard method which assumes isotropy, results in spurious
dependence of the extracted multiplicities on TKE and VCN. For the mass-partition, these biases were found to be
non-existent.
20
[1] J. Cabrera et al., Phys. Rev. C68 (2003) 034613.
[2] J. Cabrera et al., Raport CYCLONE 2002.
[3] I. Tilquin et al., Nucl. Instr. And Meth. A365 (1995) 446.
[4] Th. Keutgen, PhD Thesis, UCL (1999).
[5] D.J. Hinde et al., Phys. Rev. C39 (1989.) 2268.
[6] J. Newton et al., Nucl. Phys. A483 (1988) 126.
[7] D.J. Hinde et al., Phys. Rev. C45 (1992) 1229.
[8] V.E. Viola et al., Phys. Rev. C31 (1985) 1550.
[9] D.J. Hinde et al., Nucl. Phys. A472 (1987) 318.
3.2. Isotropy of the neutron emissions in and out of the reaction plane and
the parametrization of their angular distribution
Th. Keutgen, J. Cabrera, Y. El Masri, Ch. Dufauquez, V. Roberfroid, I. Tilquin, J. Van Mol (FNRS and Institut
de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium); R. Régimbart
(Laboratoire de Physique Corpusculaire de Caen, France); R. J. Charity (Washington University, USA); J. B.
Natowitz, K. Hagel, R. Wada (Texas A&M University, USA) and D. J. Hinde (The Australian National
University, Australia)
Résumé : Ce travail met en évidence l’isotropie dans le repère de la source émettrice de l’émission neutronique
dans le plan et hors du plan de la réaction associé au processus de fission dans les réactions
20
Ne+169Tm entre 8 et 16 MeV/nucléon. S’appuyant sur cette observation, on peut également montrer
l’effet dévastateur de sélections appliquées sur la vitesse de recul du noyau composé dans le but, par
exemple, de sélectionner les événements associés à la fusion complète. Le résultat de ce type de
sélection est l’observation d’une apparente anisotropie de l’émission neutronique. Une
paramétrisation de cette anisotropie est proposée dans ce travail.
3.2.1. Isotropy of the neutron emission in and out of the reaction plane
In Ref. [1], it was shown, after a detailed analysis, that the neutron emission characteristics (νni and Tni)
extracted from the fit of the data of all the DEMON detectors set in a 4π geometry (0 ≤ φn < 360°) were very
close to those determined by fitting only the data for the detectors set in the reaction plane (φn = 0° or φn =
180°). In order to investigate this assumption more deeply, a fit to the neutron angular distribution dνn/dΩ was
performed for the reaction 20Ne+169Tm at E =16 MeV/nucleon using only the detectors in the reaction plane (φn =
0° or φn = 180°). The parameters extracted from this type of fit (νni and Tni) were then applied to predict the
distributions out of the reaction plane. These distributions (solid curves) are presented in Fig. 1 and compared to
the experimental values (solid circles).
For the dashed curves, empirical normalization factors (see below) were applied on these curves to
achieve, when needed, the best comparison with each experimental distribution. One can directly observe that
these correction factors are very small and had to be applied for only few φn planes. In fact, the results without
correction can already be considered as good.
This study was extended by integrating, over θn angles, the resulting angular distribution with (k≠1) and
without (k=1) the correction factors, i.e. :
π dν
dν n
(φ) = k ∫ n ( θ, φ) sin θ d θ
dφ
0 dΩ
The results of these integrations are plotted in Fig. 2 for the 20Ne+169Tm reaction at the four projectile
energies.
21
Figure 1.
Figure 2.
In Figure 2, the solid circles represent the φn evolutions of dνn/dφ without corrections. The results with
corrections are represented by the open circles. In principle, any observed difference between these two set of
data points suggests the occurrence of an anisotropy in the neutron emission in and out of the reaction plane. For
each bombarding energy, the solid lines are the results of the best fit to the solid circles data using the following
expression :
dν n
(φ) = A + Bexp ( Csin φ)
dφ
where A, B and C were taken as free parameters. The values resulting from these fits are listed in Table
1. The dashed lines in Fig. 2 results from fits to the corrected data (open circles) by a same equation, but with an
extra exp(D sin2(φ)) term. The resulting function can thus be written :
dν n
( φ) = A + Bexp ( Csin φ + D sin 2 φ)
dφ
In this case D is the only parameter to be adjusted, i.e., the values of the parameters A, B and C are held
fixed at their values obtained in the original fit. The four parameters, extracted from both fits, are listed in
Table 1.
Reactions
Tm08
Tm10
Tm13
Tm16
A
2.299
2.334
2.810
2.810
B
-1.175
-1.075
-1.186
-1.050
C
0.414
0.419
0.446
0.449
D
0.009
0.023
0.008
0.024
Table 1.
Following our approach, the correction factor exp(D sin2φ) accounts for the eventual anisotropy of the
angular distribution of the neutron emission out of the reaction plane compared with the emission in the reaction
plane. Still, with the experimentally extracted small D values, one does not have to justify any important
anisotropy in the neutron emission out of the reaction plane even at φn = 90°.
22
3.2.2. Effects of the CN recoil velocity on the neutron emission in and out of the
reaction plane
It is of interest to go back to the CN recoil-velocity distribution (see the previous contribution in the
same annual report) and investigate any VCN effect on the neutron emission isotropy. In fact, if a given selection
on the CN recoil velocity destroys the isotropy of the neutron emission, we should be able to observe this effect
in such an analysis. In order to investigate this, we have applied such an analysis on the data of the E = 16
MeV/nucleon 20Ne + 169Tm reaction selecting higher values of VCN, larger than 90% of the expected value for
complete fusion process as shown in Fig. 3. Such a selection may be justified in order to isolate complete-fusion
events. The consequences of this selection on the neutron angular distributions in and out of the reaction plane
are displayed in Fig. 4.
Figure 3.
Figure 4.
The same procedure as in Fig. 1 was followed resulting in the anisotropy displayed in Fig.5. If we
compare Figs. 4 and 1 for the reaction plane (φn = 0° and 180°), the selection of the high component of the CN
recoil-velocity distribution leads to an important increasing of the neutron yields at backward angles (θn > 90°).
In fact, in order to fit these data points, the prescission neutron multiplicity has to be artificially increased. In
contrast, the postscission neutron multiplicities must be artificially decreased. Figure 5 should be compared to
Fig. 2 for the E = 16 MeV/nucleon data. One observes that the behavior of the open circles, displaying the
induced anisotropy of the neutron emission out of the reaction plane, is still very close to the original behavior in
Fig. 2 without any VCN gate.
In contrast for the solid circles constructed with the assumption of isotropic neutron emission, the
dνn/dφ (φ) distribution is more flat and strongly overestimates the values at the planes φ = 90° and 270° where
the prescission neutron emission dominates.
Figure 5.
These figures clearly show that any selection applied on the CN recoil velocity affects the isotropy of
the neutron emission in fusion-fission reactions such as 20Ne + 159Tb and 20Ne + 169Tm between E = 8 and 16
23
MeV/nucleon, and especially for the prescission neutron emission which dominates around φn = 90°. With this
VCN gate, the standard formalism used to extract multiplicities and effective temperatures [1] becomes completely
inappropriate.
[1] Th. Keutgen, PhD Thesis, UCL (1999).
3.3. Neutron-skin effects in the mirror reactions
116
Sn between 6 and 7 MeV/nucleon
58
Ni +
122
Sn and
64
Ni +
V. Roberfroid, L. Lebreton, J. Cabrera, Th. Keutgen, I. Tilquin, A. Ninane, C. Dufauquez, Y. El Masri (FNRS
and Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium); R.
Régimbart (LPC of Caen, France); J.B. Natowitz (Cyclotron Institute of Texas A & M University, USA) and R.
J. Charity (Department of Chemistry, Washington University, St. Louis, USA)
Résumé : L’utilisation de noyaux magiques en protons, tant pour le projectile (Z=28) que pour la cible (Z=50),
permet d’isoler un éventuel effet de peau de neutrons dans les réactions 58Ni + 122Sn et 64Ni + 116Sn.
L’objectif est l’étude, à l’aide de ces réactions, de l’éventuel effet de ces neutrons sur : d’une part, la
section efficace de fusion, la compétition entre la fusion-évaporation et la fusion-fission, les collisions
très inélastiques et d’autre part, sur les multiplicités de particules légères associées, neutres ou
chargées. Ces données expérimentales ont été comparées à des modèles théoriques dynamique
(HICOL) et statistique (GEMINI). Notre étude confirme que, à des énergies de projectiles d’environ 6
MeV/nucléon, il n’y a pas d’influence de la voie d’entrée sur la formation et sur la désexcitation du
noyau composé produit dans ces réactions.
3.3.1. Introduction
It has been proposed that in order to produce nuclei far of the valley of stability one should utilize
reactions induced by nuclei having “neutron skins” [1]. Indeed, it is generally recognized that some nuclei, such
as 64Ni and 122Sn, which are proton magic and neutron-rich, have a neutron skin [2-4]. The effect of such a skin
has been extensively studied in the Ni+Sn systems for energies above and below the fusion barrier [3-9]. From
these various investigations, it appears that there is a significant decrease in the effective Coulomb barriers for
collisions induced by neutron-rich isotopes such as 64Ni or 122Sn at near-barrier energies and thus an increase of
the fusion-evaporation cross sections [5]. It also seems that the neutron exchange is larger and faster using these
nuclei to equilibrate the N/Z ratio.
The first goal of this work was to determine any eventual advantage of using a neutron-rich projectile
Ni on 116Sn at around 6 MeV/nucleon to produce a 180Pt compound nucleus (CN) compared to the 58Ni + 122Sn
entrance channel. The second goal was to analyse the influence of the entrance channel on the CN decay.
Therefore, in order to isolate any neutron-skin effect, the beam energies for the two entrance channels were
chosen to produce the 180Pt (CN) either at equal excitation energy (E*=122 MeV) or with similar angular
momentum distribution.
64
For this purpose, the reactions 58Ni + 122Sn at 375.5 (b375) and 354 MeV (b354) and 64Ni + 116Sn at
382.5 MeV (b382) were investigated. We measured the cross sections for fusion-evaporation, fusion-fission, and
thus total fusion, and the multiplicities of the emitted neutrons, protons and α particles [10]. Using this set of data,
we have compared our results with the calculations of two simulation codes : HICOL (a dynamical model) [11]
and GEMINI (a statistical model) [12].
3.3.2. Experimental setup
The detection systems consisted of (see [10] for details) :
• Two large-area position-sensitive, X and Y, multiwire proportional gas counters (MWPC1,2) to detect and
characterize the fission fragments (FF).
• Two micro-channel-plate-Si detector assemblies (R1,2) to detect and characterize fission fragments and
evaporation residues (ER).
24
• Six triple-Si telescopes (T1-T6), positioned at backward angles, to detect and characterize light charged
particles (LCP).
• 96 DEMON liquid scintillator counters to detect and characterize neutron emission (n).
3.3.3. Experimental results
3.3.3.1. Evaporation residues and fission cross sections
Recalling our annual report of CYCLONE 2000, the velocity distributions of the ERs in both reactions
were simulated using a Monte Carlo code and compared with the experimental results to extract the fusionevaporation cross sections. While the mass distributions of the FF were adjusted to extract the fusion-fission
cross section.
These results are listed in Table 1:
Experiment
σ (fusion-fission)
(b)
σ (fusion-evaporation)
(mb)
σ (fusion)
(b)
b375
1.45 ± 0.13
50 ± 4
1.5 ± 0.13
b382
1.4 ± 0.13
50 ± 8
1.45 ± 0.13
Table 1 : fusion-fission, fusion-evaporation and total fusion cross section for both reactions.
From Table 1 it appears that there is no evident entrance channel influence (within the uncertainties) on
the total fusion cross sections σ (fusion) and on the competition between the fusion-evaporation and the fusionfission processes. The experimental values σ(fusion-evaporation) are in agreement with the reported data by
Freeman et al. [5]. In contrast, the extrapolation of the experimental values of σ (fusion-fission) as reported by
Lesko [13] and Wolfs [14] at our beam energy domain seems to be much lower than ours and more in agreement
with fusion static models [15]. This is due to our difficulty to separate fission, Deep Inelastic Collision (DIC) and
Quasi-Elastic (QE) in our experimental data.
3.3.3.2. Neutron, proton and α multiplicities
We have extracted, as described in our annual report of CYCLONE 2001 and in the reference [10], ν pre
n ,
post
pre
pre
post
ν post
n , ν p , ν p , ν α and να , the pre- and post-scission multiplicities of neutron, proton and α particles
respectively, from the analysis of the data associated to the DEMON detectors and to the six Si triple-telescopes.
The results are reported in Table 2.
Experiment
ν pre
n
b375
3.2 ± 0.16
0.26 ± 0.03 0.16 ± 0.02
2.3 ± 0.2
0.26 ± 0.03 0.19 ± 0.02
b354
3.0 ± 0.15
0.16 ± 0.02
0.1 ± 0.01
2.0 ± 0.2
0.17 ± 0.02 0.06 ± 0.01
b382
3.0 ± 0.12
0.16 ± 0.02 0.11 ± 0.01
1.9 ± 0.2
0.23 ± 0.02
ν pre
p
ν αpre
ν post
n
ν post
p
ν αpost
0.1 ± 0.01
Table 2 : Pre- and post-scission neutron, proton and α multiplicities in the three studied reactions.
Uncertainties are only statistical.
One can observe that there is no clear evidence of any neutron skin effects (within the uncertainties) on
the decay of the 180Pt compound nucleus. This assertion is indeed confirmed by a balance energy calculation [10].
25
3.3.4. Simulations
3.3.4.1. Dynamical calculations
The code HICOL [11] describes, as a function of time, the evolution of the nuclear interactions between
the projectile and the target during a collision. However, this code does not describe the subsequent decay of the
CN by fission or by particle evaporation. The reactions simulated by the code, are thus primarily quasi-elastic or
deep-inelastic reactions.
Fast fission may be considered, in this dynamical code, as resulting from a completely damped DIC
with a large number of exchanged nucleons.
This code allowed us to affirm that our selected fission events were mixed with an important
contribution of DIC events with angular momenta smaller than 150 ħ. Table 3 lists the cross sections of total
“fusion”, as predicted by HICOL simulations, including the DIC. The experimental values and the values
predicted by the static fusion model of Wilcke [15], are also listed in this Table. One can observe an excellent
agreement between the experiment and the HICOL predictions.
σ fusion + DIC
HICOL
(b)
σ fusion + DIC
Experiment
(b)
σ fusion
Wilcke
(b)
b375
1.47
1.50 ± 0.13
0.82
b354
1.56
b382
1.45
Experiment
0.87
1.45 ± 0.13
0.94
Table 3 : Total fusion cross sections measured in the experiments and predicted with HICOL
and the static model of Wilcke [15].
3.3.4.2. Statistical-Model calculations
The code GEMINI [12,16] is a statistical Monte-Carlo code which simulates the decay of a compound
nucleus of a given angular momentum and excitation energy. Although GEMINI cannot predict the total cross
section of fusion, it can calculate the fusion-evaporation cross section and the pre and postscission multiplicities
of all emitted light particles.
We have simulated our reactions with GEMINI code, but for only the symmetric mass partition of the
two FF. However, even in this case, the corresponding events are still mixed with DIC or fast fission. In order to
take this into account, the simulations were performed for two regions in the angular momentum space (as
already used in Ref. [17]). In the region 1, it was assumed that the CN is spherical for conventional fission which
is allowed in the angular momentum range l < lBf=0 (where lBf=0 is the angular momentum at which the fission
barrier is predicted to vanish in the calculations of Sierk [18]). The region 2 is associated to larger l-waves (lBf=0 <
l < 100 ħ) where the CN was assumed deformed.
In the GEMINI code three input parameters have been adjusted to reproduce our experimental data :
• τ1 and τ2 : fission dynamical delay times, associated to the region 1 and 2 respectively, to be added to the
standard lifetime of the CN before its scission.
• af /an : the ratio of the nuclear level density parameter at the saddle point to the level density parameter at the
equilibrium point.
The value of an was taken equal to A/9 MeV-1 and the initial excitation energy was assumed to
correspond to the full momentum transfer reaction i.e. complete fusion. In a pure and standard statistical-model
code, these parameters should be : af /an =1 and τ=0. However, to take into account the dynamical aspect of the
CN decay, these parameters were modified. Moreover, to take into account for the contribution of the fast-fission
process, the simulated pre and postscission multiplicities values were calculated as a weighted average :
26
νi =
ν1i .σ1 + ν i2 .σ 2
σ1 + σ 2
where ν1i and ν i2 are the simulated multiplicity values from region (1) and (2), respectively. They are
function of their corresponding dynamical delay time τ1 and τ2 and function of af /an, while σ1 and σ2 are the
cross sections associated with the two investigated angular momentum regions.
Following this procedure, the best parameters τ1, τ2 and af/an found to reproduce our experimental
fusion-evaporation cross section and neutron pre and postscission multiplicities were extracted and are listed in
Table 4.
af /an
τ1 = τ2 (10-21 s)
b375
1.17 ± 0.03
70 ± 5
b354
1.17 ± 0.03
70 ± 5
b382
1.13 ± 0.03
40 ± 5
Table 4 : Values of the parameters af /an, τ1 and τ2 obtained from fitting the experimental
fusion-evaporation cross sections and the neutron pre and postscission multiplicities.
It appears that τi and af /an values are very high as compared to the reported values in Refs [17,19]. The
effect of such a large value of af /an on the fission cross section is equivalent to a decrease, by 30%, of the Sierk
fission barriers used in the GEMINI code. In fact, such a decrease is needed to increase the conventional fission
probability of the CN and thus to reproduce our low experimental fusion-evaporation cross sections (50 mb). In
the same way, τi have to be large in order to reproduce the large neutron multiplicities emitted from CN with
high angular momentum. This is apparently due to the presence of a significant deep-inelastic contribution,
indistinguishable from fusion-fission events. Indeed, HICOL predicts that DICs are present in symmetric fission
[10]
. This characteristic becomes more important when projectile and target have similar masses. This may be the
reason why GEMINI reproduces very well experimental data for systems like 20Ne+159Tb and 169Tm at
comparable beam energies [17] but does not work reasonably for the Ni+Sn systems.
3.3.5. Conclusion
The cross sections of fusion-evaporation and fusion-fission have been measured for the two following
reactions : 58Ni + 122Sn at 375.5 MeV and 64Ni + 116Sn at 382.5 MeV. The cross sections of fusion-fission
obtained using detectors R1 and R2 or the MWPC's were in agreement, but clearly higher than the predictions
based on the static fusion model of Wilcke. These observations could be explained by the presence of deep
inelastic events mixed with fission. Such an affirmation was demonstrated using the dynamical code HICOL.
In contrast to the fission fragments, the evaporation residues were well separated from the other
processes. Using a simulation taking into account the angular and energy stragglings of ions in the target
thickness, the cross sections of fusion-evaporation were determined from the fit of the velocity distribution of the
evaporation residues. The results (50 ± 8 mb) for both reactions, suggest no influence of the entrance channel on
the competition between fusion-evaporation and fusion-fission around 6 MeV/nucleon. At energies near the
Coulomb barrier, the results from Freeman et al. [5] indicated a larger cross section of fusion-evaporation for the
64
Ni + 116Sn reaction in favor of a neutron-skin effect at low bombarding energies. As a general conclusion, our
results suggest that the neutron-skin effect on the fusion and on the competition between fusion-fission and
fusion-evaporation disappears when the projectile energy largely exceeds the Coulomb barrier.
The neutron multiplicities associated with the CN and the two FF decays were determined using the
DEMON multidetector array for fission-like events. The results indicate that there is no multiplicity difference
between the two reactions leading to the same CN with equal excitation energy, i.e. 58Ni + 122Sn → 180Pt (E *=
122 MeV) and 64Ni + 116Sn → 180Pt (E* = 124 MeV).
27
In conclusion, we can confirm that the decay of the CN, produced by these reactions, is completely
independent from their entrance channels.
To compare our complete set of data with theoretical predictions, the statistical code GEMINI was used
. The new version of this code takes into account the deformation effect on the CN decay. A set of initial
parameters in the code allowed us to reproduce our experimental data. However, the resulting values, i.e. af/an
=1.17 and τ = 70 zs in the reactions b354 and b382, are unexpectedly larger than previously published results
[13,17]
. This comes from the important presence of DIC in the fission events which cannot be simulated by this
code. This analysis suggests the need for a dynamical-model code such HICOL capable of taking into account
the evaporation of light particles and the fission probabilities like GEMINI.
[12]
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
N. Wang et al., Phys. Rev. C67 (2003) 024604.
G. A. Lalazissis et al., Phys. Rev. C57 (1998) 2294.
S. Ghosh et al., Phys. Rev. C49 (1994) 1059.
D. Vretenar et al., Phys. Rev. C61 (2000) 064307.
W. S. Freeman et al., Phys. Rev. Lett. 50 (1983) 1563.
A.M. van den Berg et al., Phys. Rev. Lett. 56 (1986) 572.
R.R. Betts et al., Phys. Rev. Letters 59 (1987) 978.
C.L. Jiang et al., Phys. Rev. C57 (1998) 2393.
H. Esbensen et al., Phys. Rev. C57 (1998) 2401.
V. Roberfroid, PhD Thesis, UCL (2003) and V. Roberfroid et al., Phys. Rev. C69 (2004) 044611.
H. Feldmeier, Rep. Prog. Phys. 50 (1987) 915.
R.J. Charity, Nucl. Phys. A457 (1986) 441.
K.T. Lesko et al., Phys. Rev. Lett. 55 (1985) 803.
F.L. H. Wolfs et al., Phys. Rev. C36 (1987) 1379.
W. W. Wilcke et al., At. Data And Nucl. Data Tab. 25 (1980) 389.
R.J. Charity et al., Phys. Rev. C67 (2003) 044611.
J. Cabrera et al., Phys. Rev. C68 (2003) 034613.
A.J. Sierk, Phys. Rev. C33 (1986) 2039.
J.O. Newton et al., Phys. Rev. C42 (1988) 1772.
3.4. Production of neutral and light charged particles in the proton and
alpha induced reactions on natSi between 20 and 65 MeV
Ch. Dufauquez, Th. Keutgen, J. Cabrera, V. Roberfroid, A. Ninane, J. Van Mol, Y. El Masri (Institut de
Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium), R. Régimbart (LPC, Caen,
France)
2
Résumé : Des mesures ont été effectuées afin de déterminer les sections efficaces « inclusives » ( d σ , dσ ,
dΩdE dE
dσ et σ ) de production de particules neutre et chargées légères (n, p, d, t, 3He, α et Li, Be) induites
tot.
dΩ
par des faisceaux de protons de 26.5, 48.5 et 62.9 MeV et d’alpha de 25.4, 45.5 et 57.8 MeV sur une
cible de Silicium naturel. Ci-dessous sont rapportées les derniers résultats obtenus sur la
2
détermination des sections efficaces doublement différentielles d σ ainsi que la méthode d’analyse
dΩdE
"semi-phénoménologique" pour l’obtention des sections efficaces différentielles en angle dσ .
dΩ
This year our activity was focused on :
a) The extraction of the energy spectra of the light charged particles (LCP) (p, d, t, 3He, α and 6Li, 7Li and 7Be)
from the data measured in the alpha induced reactions on natural Silicon target at 25.4, 45.5 and 57.8 MeV
beam energies;
b) The definition in the data sorting of unambiguous regions of interest for each type of detected LCP in the SiCsI (40 µm and 33 mm thick CsI) double-telescopes used in the (p, natSi) experiments. Note that we have
28
used Si-Si-CsI (40, 718, µm and 33 mm thick CsI) triple-telescopes to detecte LCP at the forward angles in
the (α, natSi) experiments (see annual report 2002) ;
c) The finalisation of all LCP energy spectra by taking into account the background substractions and the
influence of the hydrogen present on the Silicon target surfaces (see annual report 2002) ;
d) The research of some theoretical predictive codes ( such those based on the intra-nuclear cascade model or
the exciton model) and other previously published experimental data in order to make some comparisons
with our present results. Up to now, there are no available theoretical predictions and even no experimental
results to be compared to our (α, natSi) reaction results;
e) The analysis of the experimental neutron data measured in these two experiments.
We have presently determined the laboratory double–differential cross sections for all the LCP (p, d, t,
He, α and even 6Li, 7Li and 7Be) detected over a large angular distribution with respect to the beam axis (from
10° to 160° in steps of 10°) for the (p, natSi) reactions at 26.5, 48.5, 62.9 MeV and (α, natSi) reactions at 25.4,
45.5, 57.8 MeV.
3
(MeV)
nat
(MeV)
nat
(n, xt)
(n, xt)
(MeV)
(MeV)
nat
at 62.9 MeV (Ours) at 60° angle
[1]
[2]
nat
Particle energy (MeV)
Figure 1.
29
[3]
2
Figure 1 displays the laboratory d σ
dΩdE
at 60° detection angle for
nat
Si(p,xp), (p,xd), (p,xt), (p,x3He)
and (p,xα) reactions at 62.9 MeV incident proton energy. These results (black histogram) are compared to the
theoretical predictions (green solid lines) of Chadwick-GNASH computer code [1]. Two sets of comparable
experimental results are also shown as squares (in red) for the (p, 27Al) reaction [2] and as crosses (in blue) for the
(n, 28Si) reaction [3]. The GNASH code predicts relatively well the proton and alpha emission spectra but has
serious difficulties to estimate the deuteron emission. Unfortunately this code does not predict any triton and 3He
emitted particles. From the (p,27Al) reaction, using a target nucleus neighboring the 28Si, one can notice in
Figure 1 a good similarity and overlap between the different particle energy spectra. If we compare the data of
the proton and neutron induced reactions on 28Si at the same beam energies, the agreements in the deuteron and
alpha emission spectra are also good. The difference in amplitude observed in the proton secondary particle
spectra resulting from our experiment and the (n, natSi) reaction is expected and can be easily explained [4]. One
can also notice the very good symmetry by charge exchange if we consider the 3He and triton spectra as
respectively induced by the proton and the neutron incident beams on natSi targets.
Figure 2 displays the comparison between the experimental double-differential cross section (black
histogram) and the theoretical predictions (red full curve) of Talys code [5] for the proton particles detected at 25°
lab. angle in the natSi(p, xp) reaction at 62.9 MeV. Talys code predictions have been transformed from the
center-of-mass frame to the laboratory frame assuming a two-body reaction kinematic. One can notice the fair
shape agreement with the experimental data as for the direct and the preequilibrium regions. Unfortunately this is
less obvious for the proton evaporation contribution (blue dashed line). Note that Talys code does not predict the
elastic scattering contribution.
nat
Si(p,xp) 62.9 MeV
θlab.= 25°
ground state and
coulomb elastic
scattering events
28
experimental energy
threshold
evaporation
contribution
Si first excited
states
total
preequilibrium
contribution
Figure 2.
The following step in the LCP analysis was the extrapolating of all the particle energy spectra below the
experimental detection energy threshold in order to determine the differential angular cross sections dσ by
dΩ
energy integration over the entire energy ranges. This energy threshold generally corresponds to the minimum
energy for a particle to pass through the first stage Si-diode of the different telescopes (40 µm Si thick at forward
angles and 80 µm Si thick at backward angles).
This low energy extrapolation was based on LCP spectrum description assuming particle emission
resulting from the sum of different moving sources of given velocities in the laboratory frame [6]. Figure 3
displays a moving multi-source fit for the proton and alpha energy spectra as induced by 62.9 MeV protons on
nat
Si. Each energy spectrum is adjusted assuming, at least, two moving-source contributions: a) a surface
emission source called "equilibrium" to estimate the particle evaporation contribution (blue curve) and b) a
"prompt" or "preequilibrium" source moving with a velocity near one-half the beam velocity and characterised
by a volume emission type (green curve). At the most forward angles, it appears necessary to introduce an
30
additional "projectilelike preequilibrium" source (brown curve) moving with a source velocity near the beam
one. We attribute the need for this source to the emission of particles from the projectile early in its stopping
process. This volume type emission source allows the adjustement of the high energy LCP tails. The
"projectilelike" component drops off in angle very quickly as compared to the "prompt" source. We only
accounted for this third source in the fit of the proton energy spectra (Figure 3a) while the "projectilelike"
component was completely neglected in the alpha spectra. Note that the direct reactions contributions (pick up,
stripping, …) were not adjusted. The lower energy limit of this region was estimated to about 50 MeV for
proton spectra induced by the 62.9 MeV proton beam.
(b)
(a)
Figure 3.
Figure 4 displays, as a function of the lab. detection angle, the angular distribution of the energy
integrated double-differential spectra for each source component. At backward angles the preequilibrium (pree.)
contributions in the alpha spectra appeared to be very small as compared to the corresponding evaporation
contribution. In general the alpha spectra are dominated by the evaporation contribution. For the proton spectra
the "total preequilibrium" contributions (prompt + projectilelike pree.) are more dominant and display a very
steep angular dependence as compared to the "equilibrium" or evaporation source which has nearly isotropic
emission.
Figure 4.
31
Following this energy spectra type decomposition we have been able to estimate (down to the energy
emission threshold) the differential angular cross sections dσ for all the charged particles detected in our
dΩ
experiments. The future step in our analysis will be the evaluation of the total production cross sections σtot for
each type of LCP.
[1] ICRU Report 63, Bethesda, MD, 2000).
[2] F.E. Bertrand and R. Peelle, ORNL-4799, UC-34-Physics (1973)
[3] S. Benck et al., Nucl. Sci. Eng. 141 (2002) 55.
[4] S.Benck et al., Phys. Rev. C58 (1998) 1558.
[5] A.J. Koning and S. Hilaire (private communication).
[6] D. Prindle et al., Phys. Rev. C 58 (1998) 1305.
3.5. Study of proton-induced fission of actinide nuclei between 20 and 80
MeV bombarding energies
D. Belge, Ch. Dufauquez, Y. El Masri, Th. Keutgen, A. Ninane, R. Prieels, and J. Van Mol (Institut de Physique
Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium); R. Charity (University of
Washington, St Louis, USA)
Résumé : La fission des actinides induites par des neutrons et protons de moyennes et basses énergies
représente un intérêt considérable pour la compréhension des mécanismes de fission ainsi que pour la
recherche appliquée telle la transmutation des déchets radioactifs de long temps de vie issus des
centrales nucléaires. Comme première étape d’une recherche à long terme auprès du cyclotron de
Louvain-la-Neuve, nous venons de mesurer la fission induite par protons de 26.5 et 62.9 MeV sur des
cibles de 238U and 239Pu. L’analyse est en cours, des mesures identiques sur d’autres actinides sont
prévues.
3.5.1. Introduction
Nuclear waste originating from nuclear power plants have been a source of concern to the general
population for a long time. A first solution to this problem, consisting of deep geological disposal with or
without reprocessing, has been recently studied [1]. However, this solution will not attenuate the radiotoxic
inventory which is still growing. Meanwhile, the proposition has been raised that the radiotoxicity should be
reduced over time by burning the long-lived actinides waste in a nuclear-reaction process.
We have proposed, as a first step of a long-range program, cross section measurements for protoninduced fission of 238U and 239Pu nuclei at 26.5 and 62.9 MeV incident proton energies. As it is already
established, the proton-induced fission cross-section on 238U may be considered as a standard data which can be
used to check our detection system, efficiency and data-analysis methods. In coincidence with the fission
fragments, the multiplicities, energy and angular distributions of the emitted neutrons are measured at Louvainla-Neuve, for both targets, using DEMON neutron array [2].
3.5.2. Experimental setup
The experimental setup was already described in several papers [3,4]. Three different types of detectors
are used. i) Two microchannel-Si diode detector assemblies GJ1 and GJ2 measure, in single mode at different
laboratory angles, the time-of-flight and the energy, and thus, the mass of the fission fragments (FF) emitted by
the target. ii) Simultaneously, two X and Y position sensitive Multi-Wire Proportional gas Counters (MWPC),
located on both sides of the target, detect the coincident FF emitted back to back in the center-of-mass frame. iii)
Around the reaction chamber, up to 96 liquid-scintillator cells at 2 m from the fissioning target allow the
determination of the neutron energy and angular distributions associated with the fission process.
Both targets, 238U (106 µg/cm2) and 239Pu (180 µg/cm2, are "sealed" between two 12C foils, thick enough
(50 µg/cm2) to stop either the recoiling target nucleus or the evaporation residues of the induced reactions but not
the FFs. In order to monitor the reaction-chamber residual activity (eventual contamination from the target), two
thin Si detectors, shielded from the target by thick aluminum blocks, allow the detection of the 5 MeV alpha
particles emitted by any U or Pu eventual contamination on the reaction chamber wall.
32
3.5.3. Fission fragment mass distributions
Since the MWPC detectors cannot determine kinetic energies, an iterative procedure is applied to
extract the FF mass partition taking into account the energy losses of the FF in the target. To achieve this goal
and correctly identify the primary FF mass we need also to evaluate the mean post-scission neutron multiplicity
emitted from each fragment before leaving the target. This can be obtained, on average, from the neutron angular
and multiplicity distributions included within the DEMON data set. After some iterative loops, this procedure
should converge in a correct FF mass determination, which can be checked by comparison with the mass
distribution extracted from the GJ1 and GJ2 detectors. The full procedure has not yet been applied to our raw
data shown in Fig. 1.
Figure 1 :
Preliminary FF mass distribution, using MWPC’s, for proton-induced fission on
U and 239Pu at two proton beam energies, i.e. 26.5 MeV (left panels) and 62.5
MeV (right panels).
238
Since 238U data are used to certify the quality of the applied procedure, we show in Fig. 2 a comparison
of our ”crude” first results with the published ones from the Uppsala [5] facility. An improvement is expected
when the full data analysis procedure is applied.
Figure 2 : Preliminary FF mass distributions (solid thick black lines) obtained from proton
induced fission on 238U at 26.5 and 62.9 MeV bombarding energies. These data
are compared to Uppsala published results taken at 20 MeV (thin solid line) 35
MeV (dotted line on the left side panel) and 60 MeV (dotted line on the right side
panel).
33
3.5.4. Prospectives
Apart from the mass distribution of FF, the associated neutron multiplicities are also important. This is
inherently part of the analysis and matches well with the possibilities of the DEMON detectors in the Louvainla-Neuve setup. Table 4 shows the scarceness of this kind of data in the actinide region.
As it was announced in the beginning of this program, we will extend these measurements to new
actinide nuclei such as 237Np, 232Th and 241Am using the same experimental setup and the same proton beam
energies (26.5 and 62.9 MeV). Again the target thickness will range between 120 and 150 µg/cm2 with a 50
µg/cm2 carbon backing on each of their sides.
Ref.
EXFOR
Ep
#tot
σ(p,f)
Mff
(p,xn)
10-80
11
8
5
1
10-80
12
11
3
12-80
2
2
1980-1991
20-80
1
2
1991
U
65
1
Th
9-22
1
1
1
1991
U
8-25
1
1
1
1991
10-32
1
1
1
1991
10-18
1
1
1
1991
Am
9-16
1
1
1
1991
U
20-60
1
1
1
Targets
232
Th
233-238
U
237
Np
239
Pu
HINDAS
Ohtsuki
238
232
237
Np
239
Pu
241-243
Rubchenya
238
ν
Dates
1980-1996
1980-1991
in progress
1
1
2001
Table 1 : Presently available data on proton-induced reactions on actinide targets between 10 and 80
MeV. Ep stands for the proton energy; #tot for the total number of experiments; σ(p,f), Mff,
(p,xn), ν for the number of fission cross section, mass distribution, xn reaction, neutron
multiplicity results respectively.
[1] G. Fioni, Private communication at Seminar in Fission, Pont d’Oye V, September 2003
[2] I. Tilquin et al., Nucl. Instr. and Method A365 (1995) 446.
[3] Rapport d’ativité 2001, UCL-IISN, p 12.
[4] Rapport d’ativité 2002, UCL-IISN, p 26.
[5] V.A. Rubchenya et al., Nucl. Instr. and Method A463 (2001) 653.
34
4.
RÉACTIONS INDUITES PAR DES NEUTRONS / REACTIONS INDUCED BY
NEUTRONS
4.1. Measurement of microscopic cross sections in fast neutron induced
reactions (En= 25 - 65 MeV) on bismuth and natural uranium
E. Raeymackers, S. Benck, I. Slypen, J.-P. Meulders (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium); N. Nica, V. Corcalciuc (Institute of Atomic Physics, Heavy Ion
Department, Bucharest, Roumania)
Résumé : Les données relatives aux sections efficaces doublement différentielles de production de protons,
deutons, tritons et particules alpha induite par neutrons rapides (En = 25 – 65 MeV) sur cibles de
bismuth et d’uranium naturel ont été comparées aux prédictions théoriques de deux codes nucléaires,
GNASH et TALYS, basés sur le modèle exciton pour la description de la partie pré-équilibre des
spectres et sur le modèle statistique de Hauser-Feshbach pour la description de l’évaporation du
noyau résiduel. Les résultats présentés montrent une nette amélioration, dans le cas du TALYS, des
résultats théoriques relatifs à la production de particules complexes par rapport à ceux du GNASH.
This year, the data relative to the measurements of secondary light charged particle emission induced by
neutron on bismuth and natural uranium target has been compared to theoretical predictions. These calculations
were done with two nuclear reaction codes, GNASH [1] and TALYS [2], both based on the exciton model to
describe the pre-equilibrium part of the spectra and the Hauser-Feshbach statistical theory for the subsequent
compound nucleus decay. Basically, the TALYS code, still under development, contains improved
phenomenological description of the composed charged particle emission[3] which brings noticeable amelioration
of the results. Only a sample of the results will be given in what follows. For further information, please see
Refs..[4] and [5].
Figures 1 and 2 show the double-differential cross-sections for respectively the proton and the deuteron
production on uranium for ten and nine incident neutron energies at 20° laboratory angle, compared to the
predictions of the two theoretical model codes.
62.7 MeV
62.7 MeV
2
1
0
0
53.5 MeV
2
0
0
49.0 MeV
2
45.0 MeV
0
2
0
2
-1
-1
d σ/dΩ dE (mb sr MeV )
d2 σ/dΩ dE (mb sr -1 MeV -1 )
49.0 Me V
1
0
41.0 MeV
2
0
37.5 MeV
2
0
34.5 MeV
2
45.0 Me V
1
0
41.0 Me V
1
0
37.5 Me V
1
0
0
34.5 Me V
1
31.5 MeV
2
0
0
28.5 MeV
31.5 Me V
1
2
0
0
25.5 MeV
10
00
20 30 40 50 60 70
Proton energy (MeV)
Figure 1 : Double-differential cross-sections (d2σ/dΩdE)
for (n,px) reactions at 20° laboratory angle, for the
indicated ten incident neutron energies (filled dots, in
bins of 2 MeV) on uranium. GNASH (dashed lines) and
TALYS (continuous lines) code calculations are shown.
28.5 Me V
1
2
00
53.5 Me V
1
10
20 30 40 50 60
Deuteron energy (MeV)
70
Figure 2 : Double-differential cross-sections (d2σ/dΩdE)
for (n,dx) reactions at 20° laboratory angle, for the
indicated nine incident neutron energies (filled dots, in
bins of 2 MeV) on uranium. GNASH (dashed lines) and
TALYS (continuous lines) code calculations are shown.
35
In the proton case, both codes give a fair description of the spectra, except for the lower incident
neutron energies for which TALYS describes better the order of magnitude of the experimental results. For
deuterons of Figure 2 (and, generally, for complex ejectiles), GNASH underestimates the double-differential
cross-sections while TALYS reproduces better, at least for the higher incident neutron energies in the deuteron
case, the order of magnitude and the shape of the spectra.
Figure 3 shows, for the four ejectiles with the bismuth target, the dependence of the total production
cross-sections relative to the incident neutron energy. These results are compared with the theoretical values
calculated by the GNASH and TALYS codes. For the alpha-particle case, the TALYS values include the very
small 3He contribution which is also included in the experimental values. A dramatic improvement is shown in
the TALYS results for complex particle emission, relative to the GNASH results.
400
40
p
20
200
σ T (mb)
t
0
0
α
d
50
100
0
20
30
40
50
60
0
20
30
40
50
60
Incident neutron energy (MeV)
Figure 3 : Experimental total cross-sections (filled dots) for (n,px), (n,dx), (n,tx) and (n,αx)
reactions on bismuth vs. incident neutron energy compared to calculated values by
the GNASH (dashed lines) and TALYS (continuous lines) nuclear reaction codes.
In the alpha-particle case, the TALYS theoretical curve includes the 3He
contribution.
In conclusion, the results relative to the two targets have been compared to theoretical predictions of
two nuclear reaction model codes (GNASH and TALYS). GNASH code describes quite well the proton results
but strongly underestimates the production of more complex particles. The TALYS code gives better results,
especially for complex ejectiles, by reproducing the shape and the order of magnitude of the spectra, except for
the very low energy part of the alpha-particle spectra (not shown here). Nevertheless, TALYS descriptions of the
complex particle angular distributions (not shown here) have to be improved by incorporating in the Kalbach’s
systematic the whole new class of recent (n,xlcp) measurements in which this work is included.
[1] P.G. Young, E.D. Arthur, M.B. Chadwick, Los Alamos National Laboratory Report No. LA-12343-MS,
(1992), GNASH-FKK version gn9cp0, PSR-0125, program received from NEA Data Bank (1999).
[2] A. J. Koning and S. Hilaire, unpublished.
[3] C. Kalbach, Users manual for PRECO-2000: “Exciton model pre-equilibrium code with direct reactions”,
Duke University (2001).
Retrieved from www.nndc.bnl.gov/nndcscr/model-codes/preco-2000/
[4] E. Raeymackers, S. Benck, N. Nica, I. Slypen, J. P. Meulders, V. Corcalciuc and A. J. Koning, Nucl. Phys.
A726, 210 (2003).
[5] E. Raeymackers, S. Benck, I. Slypen, J. P. Meulders, N. Nica, V. Corcalciuc and A. J. Koning, Phys. Rev.
C68, 024604 (2003).
36
4.2. Light charged particle production induced by fast neutrons (En = 25 –
65 MeV) on natFe
I. Slypen, S. Benck, E. Raeymackers, J-P. Meulders (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium); N. Nica, V. Corcalciuc (Institute of Atomic Physics, Heavy Ion
Department Bucharest, Romania)
Résumé : Les sections efficaces doublement différentielles de production de protons, deutons, tritons et
particules alpha induite par neutrons rapides (En compris entre 25 et 65 MeV) sur une cible de natFe
ont été mesurées à 9 angles entre 20° et 160°. L’analyse des données est à présent terminée et les
résultats sont publiés.
There is a growing request, in the last years for studies of fast neutron induced reactions especially at
higher incident energies. Since more than 10 years, our group has performed at the Louvain-la-Neuve cyclotron
several experiments dedicated to the measurement of light charged particle (proton, deuteron, triton and alphaparticle) production induced by fast neutrons on different targets: the last two ones were cobalt and iron. The
cobalt data were published in 2002 [1] and the data analysis for the iron measurement has been terminated
beginning of this year and the results are also now published [2].
Experimental data on light charged particle production in proton-induced reactions are available for 56Fe
and Fe [3] at comparable incident proton energies (28.8, 38.8 and 61.5 MeV). Our data together with those of
Ref. 3 provide complementary information on nucleon-induced light charged particle emission. This allows a
comparison of the influence of the projectile isospin on the relative magnitude of charged particle yields and
imposes a more detailed test of nuclear models.
54
d σ/dEdΩ (mb/MeV.sr)
62.7 MeV
53.5 MeV
2
49.0 MeV
45.0 MeV
41.0 MeV
Triton Energy (MeV)
Figure 1 : Double-differential cross sections for respectively natFe(n,tx) reactions (filled dots)
and 59Co(n,tx) (open dots) at 20° lab. for the indicated incident neutrons energies.
Corresponding data from proton induced reactions for 56Fe (61.5 MeV at 22°,
squares, and at 20°, stars) and 54Fe (38.8 and 61.5 MeV at 20° triangles) are also
shown. GNASH [5] and TALYS [6] calculations are presented as respectively
dashed and continuous lines.
Double-differential cross sections (d2σ/dΩdE) were measured at nine laboratory angles between 20° and
160° for protons (p), deuterons (d), tritons (t) and alpha-particles (α) at the following neutron energies: 28.5 ±
1.5, 31.5 ± 1.5, 34.5 ± 1.5, 37.5 ± 1.5 (only for protons and deuterons), 41.0 ± 2.0, 45.0 ± 2.0, 49.0 ± 2.0, 53.5 ±
37
2.5 and 62.7 ± 2.0 MeV (for the four outgoing particles). The overall relative uncertainties of the experimental
points in the spectra are about 6 %, 9 %, 20 and 25 % for respectively p, d, t and α at 62.7 MeV data. They are
mainly given by the statistics in the spectra. At lower ejectile energies, the thick target corrections (PERTEN
code [4]) contribute with supplementary uncertainties. For all the other incident neutron energies (continuum),
these values are two to three times higher as a consequence of a lower incident neutron flux. The uncertainty of
the cross section absolute scale is about 7 % at all incident neutron energies.
Fig. 1 shows the double-differential cross sections for the production of tritons (20° lab.) for the indicated
incident neutron energies. Filled dots indicate iron data in 3 MeV energy bins. Open dots represent data on
cobalt [1]. Experimental results from proton-induced reactions [3] are represented as follows: stars and squares for
56
Fe at respectively 20° and 22° laboratory angles at 61.5 MeV, and triangles for 54Fe at 61.5 and 38.8 MeV
(20°) incident proton energy. The results on iron and cobalt are in good agreement as expected for close mass
nuclei. Generally, our results are in good or fair agreement with those of proton-induced reactions for the
complex ejectiles, especially in the pre-equilibrium region. Our results have also been compared with two
nuclear reaction codes based on exciton models, the widely applied code GNASH [5] and a new code, still under
development, TALYS [6]. The dashed lines show calculations with GNASH code while continuous lines show
calculations with the TALYS code.
Figure 2 shows the energy-differential cross sections for the emission of tritons at five indicated
incident neutron energies. The results on cobalt and iron are in agreement and both the two codes describe
reasonably well the experimental data.
dσ/dE (mb/MeV)
62.7 MeV
53.5 MeV
49.0 MeV
45.0 MeV
41.0 MeV
Triton Energy (MeV)
Figure 2 : Energy-differential cross sections for (n,tx) reactions on iron (filled dots) and
cobalt (open dots) [1]. Data from proton-induced reactions on 56Fe (61.5 MeV,
stars) and 54Fe (38.8 and 61.5 MeV, triangles) [3] are shown. GNASH (dashed
lines) and TALYS (continuous lines) code calculations are presented.
[1] N. Nica et al, J. Phys. G: Nucl. Part. Phys. 28 (2002) 2823.
[2] I. Slypen et al, J. Phys. G: Nucl. Part. Phys. 30 (2004) 45-64.
[3] F.E. Bertrand and R.W. Peelle, Phys. Rev. C8 (1973) 1045 and Oak Ridge Report ORNL-4799 (1973).
[4] I. Slypen et al, Nucl. Instrum. And Methods B88 (1994) 275.
[5] P.G. Young, E.D. Arthur, M.B. Chadwick, LANL Report No. LA-12343-MS , (1992), GNASH-FKK version
gn9cp0, PSR-0125, program received from NEA Data Bank (1999).
[6] A. Koning and S. Hilaire, unpublished.
38
5. PHYSIQUE DES NANOSTRUCTURES / NANOSTRUCTURE PHYSICS
5.1. Nanoscopic superconducting slab in static electric and magnetic fields
D. Bertrand, J. Govaerts, G. Stenuit (Institut de Physique Nucléaire, Université catholique de Louvain, Louvainla-Neuve)
Résumé : L’analyse des mesures réalisées sur une tranche supraconductrice d’épaisseur nanoscopique n’a pas
permis à ce stade de conclure à la pertinence de l’extension covariante de Lorentz des équations
phénoménologiques de Ginzburg-Landau de la supraconductivité. Toutefois plusieurs phénomènes
pourraient expliquer l’écart de ces mesures avec les simulations et rendre compte de l’effet non
négligeable des charges électriques non appariées lors de l’application d’un champ électrique
externe.
5.1.1. Electrostatic potential in a covariant framework
As discussed in previous annual reports[1,2], a series of measurements have been performed in order to
discriminate experimentally between the Lorentz-covariant extension and the usual Ginzburg-Landau (GL)
theory of superconductivity[3]. These experiments showed no dependency of the superconducting state on the
external electric field, leading to an apparent failure of both models. Presumably, the explanation for this result is
the fact that some non-paired normal electrons could play a crucial role against the electric field. Specifically,
according to Lipavský et al.[4], an electrostatic potential of the Bernoulli type could combine with the
thermodynamic potential in the superconductor, resulting in an effective potential acting on the condensate of
Cooper pairs. The main consequence would be the formation of surface charge screening the external electric
field, preventing it from penetrating the superconducting condensate. One advantage of Lipavský’s expression
for the potential is that the resulting relations remain valid even far from the critical temperature.
Starting from Lipavský’s theory, a covariant generalisation has been introduced and carefully
investigated. By performing numerical expansions around solutions obtained for this system, we found that the
screening of the electric field could be observed even in a covariant theory, with physical parameters (coherence
and penetration lengths) being unfortunately far from realistic cases. Numerical simulations are still in progress,
but the extreme sensivity of the solutions to these parameters has not allowed to reach so far values
corresponding to aluminum.
5.1.2. Paraconductivity
In parallel, recent publications concerning cuprate superconducting materials discuss properties
somewhat reminiscent of another surprising characteristic of our experimental results, namely the fact that the
phase transition does not follow a sharp drop in the resistivity measurements, but a smooth decrease instead. At
first it was suggested that electric contacts made with silver paste could be responsible for this feature, but the
recent developments drew our attention to similar smeared transitions observed in the late 60’s on thin Al-films,
known as paraconductivity. This special behaviour is one of the many observable manifestations arising from
fluctuations in the density of Cooper pairs close to the transition point. A careful bibliographic survey has been
performed, and various theoretical models have been compared. In particular, one of these introduced by
Marcelja, Masker and Parks[5] could be compared with a limiting case of Lipavský’s or the covariant model,
provided a matching of the numerical parameters may be identified.
5.1.3. Four-fermion couplings
Finally, a completely different approach is presently being investigated. Considering effective fourfermion couplings in a Dirac formalism, a complete study could lead to an extended relativistic covariant BCS
theory involving electrical features and accounting at once for both the paired and unpaired electrons at finite
temperatures below the critical point, leading to the appropriate extensions of the usual Ginzburg-Laudau
effective theory.
[1] D. Bertrand et al., Rapport Annuel CYCLONE 2001, p. 46.
[2] D. Bertrand et al., Rapport Annuel CYCLONE 2002, p. 36.
[3] J. Govaerts, D. Bertrand and G. Stenuit, On Electric Fields in Low Temperature Superconductors,
Supercond. Sci. Technol. 14 (2001) 463-470.
39
[4] P. Lipavský, J. Koláček, K. Morawetz and E.H. Brandt, Electrostatic Potential in a Superconductor, Phys.
Rev. B65 (2002) 144511 (18 pages).
[5] S. Marcelja, W.E. Masker and R.D. Parks, Electrical Conductivity of a Two-dimensional Superconductor,
Phys. Rev. Lett. 22 (1969) 124.
5.2. Vortex Matter in Lead Nanowires
G. Stenuit, J. Govaerts and D. Bertrand (Institut de Physique Nucléaire, Université catholique de Louvain,
Louvain-la-Neuve); S. Michotte and L. Piraux (Institut de Physico-Chimie et de Science des Matériaux,
Université catholique de Louvain, Louvain-la-Neuve)
Résumé : Une nouvelle analyse de la magnétisation expérimentale d’un réseau de nanofils de Plomb fut
réalisée. Cette dernière confirme à nouveau le comportement non trivial à l’échelle mésoscopique de
la frontière κc ( = 1 / 2 dans un échantillon macroscopique) entre supraconducteurs de type-I et de
type-II. Au-delà d’une reproduction endéans les 10 % de marge d’erreur des données expérimentales
de la magnétisation totale des échantillons, le degré d’impureté, au sens d’un faible libre parcours
moyen des électrons, a également été isolé et corroboré par le cahier de charge de l’électrodéposition
opérée par l’expérimentateur. Enfin, l’hypothèse invoquée précédemment de la symétrie sous
rotation des solutions du modèle phénoménologique de Ginzburg-Landau indépendant du temps fut
testée pour ces échantillons et confirmée par un modèle résolvant ces équations dans le plan (r,φ) des
coordonnées cylindriques (r,φ,z).
5.2.1. Introduction
Recent developments in nanotechnologies and measurement techniques allow nowadays the
experimental investigation of the magnetic and thermodynamic superconducting properties of mesoscopic
samples far away from the critical temperature Tc[1,2]. In order to compare the magnetization curves
(magnetization versus external magnetic field at a given temperature T) of an array of lead nanowires to the
theoretical predictions, some assumptions must be considered to simplify the model.
First of all, due to the small radius of the nanowires, only the one dimensional radial Ginzburg-Landau
(GL) equations are used. Indeed, for such sizes, temperatures and κ values, the phase diagram (Bext,Energy)
exhibits only those states with a vorticity L which is strictly less than 4 since Giant Vortex states with higher
vorticity are too large compared to the radius. Nevertheless, this assumption was verified by solving the 2D-GL
equations in the (r,φ) plane of the cylindrical coordinates.
In addition, the magnetization presents a weak diamagnetic (in the L=0 state) and paramagnetic (in the
L ≥ 1 state) response in the mesoscopic limit. The mutual magnetic interactions between pairs of nanowires may
thus be neglected in our model.
Therefore, considering a Gaussian distribution for the radii of nanowires making up the array, the total
magnetization may be expressed as the sum of the magnetization of each type of nanowire multiplied by its
statistical weight.
5.2.2. Analysis of the experiments
The analysis, whose details are available elsewhere[3,4,5], involves a comparison between the
experimental and theoretical magnetization curves of lead nanowires (Tc=7.2K), with a mean radius of 120 nm
and a variance of 15 nm. These values being fixed and confirmed by scanning the SEM pictures of the alumina
matrix, the free parameters of the model are λ (the penetration depth) and ξ (the coherence length). Finally, in
order to study the hysteretic behaviour of the sample, it is worth mentioning here that the experimental
magnetization curves have been obtained when the external magnetic field (parallel to the z-axis of the
nanowires) is swept up and down after zero field cooling.
For example, Figure 1 shows experimental and theoretical results for T=5 K and T=3.25 K. Beyond the
qualitative and quantitative agreement between the curves, it should be stressed that the experimental hysteretic
behaviour due to the Bean-Livingston barrier[6] was predicted by the model, provided a new parameter is
introduced for the lowest temperatures.
40
Figure 1 : Comparison between the experimental (markers) and theoretical (solid and dotted
lines) total magnetization. From top to bottom, curves at T=5 K and T=3.25K. The
adjusted values for λ and ξ are (58,102) and (53,75) nm, respectively.
Figure 2 shows the temperature dependency of the characteristic lengths for λ and ξ, adjusted to fit the
experiments. All values agree within 10 % with the empirical laws[7],
λ (T ) =
λ0
1− t
4
and ξ(T ) =
ξ 0 (1 − 0.25t )
1− t
where t =
T
, λ 0 = 51 nm and ξ 0 = 69 nm.
Tc
Figure 2 : Temperature dependency of λ and ξ. The adjusted values (in order to fit the
magnetization curves) are in agreement with the empirical laws[7] for ξ0 = 69 nm
and λ0 = 51 nm (solid lines). The error bars represent a 10 % variation around the
given value.
By accepting the following dependencies for λ ∝ 1 / l and ξ ∝
l , in terms of the mean free path
l of the electrons, the comparison with the characteristic lengths of the first sample[3, 4] (λ0 = 46 nm and ξ0 = 74
nm) seems to indicate that the previous one was “cleaner”, namely possessed a larger value for l .
41
5.2.3. Comments and conclusions
In order to explain and reproduce within 10 % of precision the magnetic properties of the considered
lead nanowire array, only cylindrically symmetric solutions are required. In particular, the Meissner state (L=0)
and, for the lowest temperatures, the Abrikosov (L=1) and Giant Vortex (GV, L=2,3) states were experimentally
observed in these apparently type-I superconductors. However, the presence of a state with L≠0 is not surprising
since the distinction between type-I and II looses its significance at mesoscopic scales[8].
By changing the temperature of the sample in the SQUID magnetometer, we were able to modify and to
check the three characteristic regions already observed by Geim et al.[1]: the type-II behaviour for small radius,
the type-I phase transition in the Meissner state, and the vortex state with type-II phase transition from the
superconducting to normal state. Finally, it should also be stressed that the absence of jumps in state transitions
is explained by the spread in the radius values for all nanowires within the sample.
[1] A.K. Geim, I.V. Grigorieva, S.V. Dubonos, J.G.S. Lok, J.C. Maan, A.E. Filippov and F.M. Peeters, Nature
390 (1997) 259.
[2] S. Michotte, L. Piraux, S. Dubois, F. Pailloux, G. Stenuit, J. Govaerts, Physica C377 (2002) 267-276.
[3] G. Stenuit, S. Michotte, J. Govaerts, L. Piraux and D. Bertrand, Vortex Configurations in Mesoscopic
Superconducting Nanowires, Proceedings of the International Conference on Modern Problems in
Superconductivity, Yalta (Ukraine), September 9 – 14, 2002, ed. S. Kruchinin, Mod. Phys. Lett. B17
(2003) 537-547.
[4] G. Stenuit, S. Michotte, J. Govaerts and L. Piraux, Eur. Phys. J. B33 (2003) 103-107.
[5] G. Stenuit, S. Michotte, J. Govaerts and L. Piraux, Penetration and Coherence Lengths in Lead Nanowires,
in preparation.
[6] C.P. Bean and J.B. Livingston, Phys. Rev. Lett. 12 (1964) 14.
[7] M. Tinkham, Introduction to Superconductivity, 2nd ed. (McGraw-Hill, New York, 1996).
[8] G.F. Zharkov, Phys. Rev. B63 (2001) 224513.
5.3. Track etching in polymers
E. Ferain*, H. Hanot, F. Dehaye, S. Demoustier-Champagne, R. Legras (Université catholique de Louvain,
Centre de Recherches du Cyclotron et Unité de Chimie des Hauts Polymères - POLY)
Résumé : A l’unité de physique et de chimie des hauts polymères, les développements récents dans le domaine
de la technologie de “track-etching” ont porté sur la production contrôlée à l’échelle du laboratoire
de supports nanoporeux de type “track-etched”. Ces supports poreux sont utilisés notamment par
plusieurs groupes de recherche pour la synthèse de nanomatériaux polymères et métalliques
présentant des propriétés fondamentales intéressantes. Ces développements ont été réalisés dans le
cadre de projet de recherches financés par la Communauté Européenne et par la Région Wallonne;
les principaux résultats concernent la réalisation de pores de taille avoisinant les 10 nm, l’application
du procédé de « track-etching » à une mince couche de polymère déposée sur un support rigide ou
flexible, la réalisation de support “track-etched” à partir de film de polyimide résistant aux
températures élevées et la mise au point d’un procédé de « patterning ». L’étape d’irradiation des
couches polymères a été réalisée au Centre de Recherches du Cyclotron au moyen d’ions Ar 220 MeV
ou d’ions Xe 574 MeV.
5.3.1. Introduction
Previous CYCLONE annual report considered research activities about interactions between energetic
heavy ions and polymers at the ‘unité de physique et de chimie des hauts polymères’ during the last 20 years.
More precisely, generalities and most recent developments about the track etching process, consisting in an
irradiation of a polymeric material by energetic heavy ions creating linear damage tracks and followed by a
chemical etching of these tracks to pores, have been described in details. These recent developments are related
to the reproducible and controlled lab-scale production of nanoporous track etched templates made of selfsupported polycarbonate films or of polycarbonate layers deposited on a support like glass, quartz, silicone and
incorporating circuitry. These templates are intensely used by many research groups for the synthesis of micro-
*
[email protected], tel 0 10 47 35 60, fax 0 10 45 15 93
42
or nanomaterials having interesting fundamental properties and becoming an integral part of devices for specific
applications. The synthesis method, called template-base method, consists in the filling of the pores of the
templates with one or many desired materials allowing the synthesis of polymeric or metallic micro-or
nanomaterials in wires or tubules shape (Fig. 1) with a well-controlled size and shape and exhibiting a small
roughness and a large aspect ratio.
Figure1 :
Surface of a polycarbonate track etch membrane with 40 nm pore (left); these
membranes, with pore size in the range 10 nm to 10 µm can be used as template
for the synthesis of e.g. cobalt nanowires (middle) or gold nanotubes (left).
5.3.2. Activities during year 2003
During this year, main R&D works related to nanoporous track etched templates have been performed
in the frame of two research projects :
1. 'conductive nanowires for applications in microwave, magnetic and chemical sensing devices based on
polymer track etched templates'
funded by the European Community under the Competitive and Sustainable Growth Programme
(February 2000 – June 2003) ;
partners involved : UCL-POLY (R. Legras (coordinator), S. Demoustier-Champagne, E. Ferain), UCLPCPM (L. Piraux), CEA Grenoble (U. Ebels), CNRS Orsay (J.-M. George, A. Fert), Thalès (F. Nguyen
Van Dau, J.C. Mage), Epigem (T. Ryan, T. Harvey), IFPD Dresden (N. Hermsdorf, M. Stamm).
2. 'conception et réalisation de supports nanoporeux et de nanomatériaux - application à la réalisation de
dispositifs haute fréquence'
funded by the Walloon Region (September 1999 – October 2003) ;
partners : UCL-POLY (R. Legras, S. Demoustier-Champagne, E. Ferain), UCL-PCPM (L. Piraux), UCLEMIC (I. Huynen) ;
during these projects, a wide range of new nanotechnology based on heavy ion beams, templates and
nanowires have been developed. Progress in track etching technology has lead to the realisation of new
generations of templates for the preparation of magnetic and conductive nanowires; basic and specific
properties of these nanowires have been measured for further optimisation of systems as microwave
filters, magnetic switching devices, chemical and biochemical sensors,… and designs of devices for
various applications have been therefore evaluated.
More precisely for this project, key achievements related to track etched templates are the following :
track etching process has been intensely used at the lab-scale for the production of self-supported
polycarbonate templates with pore size down to 10 nm. All these samples have been distributed to
research partners and mainly used for the synthesis of nanowires or nanotubes; pore filling has been
demonstrated for pore size down to 25 nm ;
track etching process has been also adapted to the realisation of supported polycarbonate templates (Fig.
2) made of a thin layer deposited on different substrates (glass, quartz, silicon with integrating circuitry);
with similar pore size and pore filling limits as for self-supported polycarbonate template; production of
such supported templates is now usually performed at the lab-scale ;
43
Figure 2 : Schematic view of a structured templates made of a thin polymer layer deposited
above a supported and well-designed conductive circuitry; pores and hence
nanowires or nanotubes are confined into zones using patterning® process.
track etching technology has been demonstrated for other polymers than polycarbonate and important
process optimisations has been performed for polyimide film (Kapton) and supported polyimide layer;
interest of Kapton is linked to its performance in applications involving very high, 400°C, or very low, 269°C, temperature, and is used in a wide variety of applications such as substrates for flexible printed
circuits, transformer and capacitor insulation and bar code labels; as for polycarbonate, production of
polyimide template samples is now carried out at the lab-scale and first samples have been supplied to
potential end-users ;
patterning process has been improved to give 1 micron feature size in polycarbonate template and
patterning feasibility has been demonstrated on polyimide templates with a 10 micron resolution. In
parallel, a fundamental study has improved our knowledge of physico-chemical modifications induced in
polycarbonate film during all the steps of the patterning process.
Figure 3 : SEM picture showing the surface of a patterned self-supported polycarbonate
templates; 1µm square white areas correspond to porous zones where around 10
pores with a diameter of 100 nm are localised
For all this R&D works on track etching process, facilities available at the Centre de Recherches du
Cyclotron have been used for the continuous irradiation of polymer films as well as for the irradiation in static or
continuous mode of supported polymer layer. Ar ions @ 220 MeV are used for the irradiation of polycarbonatebase templates and Xe @ 574 MeV for the irradiation of polyimide-base templates.
5.3.3. Activities forecast for year 2004
In the frame of a new European funded project, we expect to continue to explore the modifications
induced in polymers by heavy ions; post-irradiation evolution of damage tracks (thermal and light illumination)
will be also considered in order to explain beneficial effects of these treatments on track etching. Track
formation in polymers like PVDF and PEEK will be also considered and track etching feasibility will be
investigated. Finally, development of polycarbonate- and polyimide-base templates for specific devices will be
carried out and track-etched templates will be prepared using existing lab-scale technology in order to supply
research partners with materials for the synthesis of metallic and polymeric nano-objects.
An important activity for the next two years will be focused on the creation of a new spin out dedicated
to the development, commercialisation and production of templates based on energetic ion track technology.
This project will enable to valorise R&D works performed at UCL during last years on second and third track
etching technologies. This company will supply structured nanotemplate polymeric materials for use as the
active components of sensing, diagnostics, analytical, measuring and processing systems; it would therefore
make products based on heavy ion bombardment and track-etching, on patterning and pore filling process, and
would seek to advance further development of applications by partnerships with third parties. Access to key
facilities (Cyclotron) and people determine that this company be based very near to the UCL.(more info
available at http://www.it4ip.be).
44
6. RADIOBIOLOGIE / RADIOBIOLOGY
6.1. Induction de l’apoptose dans des cellules normales et tumorales par les
neutrons rapides : étude des mécanismes concernés et modulation
pharmacologique
P. Bischoff (CR1 INSERM, Laboratoire de Cancérologie Expérimentale et de Radiobiologie (LCER), EA-3430
« Altérations géniques des Cancers et Réponse thérapeutique », Institut de Recherche contre les Cancers de
l'Appareil Digestif (IRCAD), Université Louis Pasteur (ULP), Hôpitaux Universitaires, BP 426, 1, place de
l'Hôpital, F-67091 Strasbourg Cedex, (France) ; Tél 33 (0)3 88 11 90 61 ; Fax 33 (0)3 88 11 90 97 (E-mail :
[email protected]))
Résumé : The purpose of our current program of experiments at CRC is 1) the analysis of some molecular
mechanisms underlying the induction of apoptosis by fast neutrons and 2) the determination of the
capacity of anticancer agents (cisplatin, oxaliplatinŠ) to reinforce the cytotoxicity of these particles
toward malignant cells. Indeed, high-linear energy transfer (LET) radiation offers promising
perspectives of application in cancer treatment (hadrontherapy). In our experiments, cancer cell lines
from various histological and presenting different sensitivity against ionizing radiation are used. They
are exposed to 65 MeV neutrons, at doses usually ranging from 2 to 16 Gy. Apoptosis is determined at
various times post-irradiation by a diversity of methods and techniques: flow cytometry, TUNEL
labelling, caspases activities, etc. The sequential activation of caspases has been analyzed in TK6 and
NH32 human lymphoblastoid cell lines and compared to that taking place after an irradiation
provided with 6 MV X-rays (Fischer et al, 2003). Recently, we have also showed that when combined
with fast neutrons, cisplatin was capable to increase the occurrence of the "premature senescence"
(which corresponds to an irreversible arrest of the cell growth) in U-87 human glioblastoma cells
(Fischer et al, 2004).
Ces recherches, initiées il y a plusieurs années déjà et qui font l’objet d’une collaboration étroite avec
une équipe du Laboratoire de radiobiologie et radioprotection (RNBT) de la Faculté de médecine de l’UCL, se
rapportent à l’étude de la cytotoxicité des neutrons rapides sur différents types cellulaires, normaux et tumoraux :
lymphocytes spléniques, lignées tumorales d’origine lymphoide, lignées tumorales obtenues à partir de tumeurs
solides, etc. Les neutrons rapides produits par le cyclotron de Louvain-la-Neuve constituent d’excellents modèles
de radiations ionisantes à transfert d’énergie linéique (TEL) élevé et, de ce fait, les études entreprises auprès de
cet accélérateur sont à même de nous renseigner sur les effets biologiques de ces particules. En outre, les
installations spécifiques mises à la disposition des chercheurs en radiobiologie : collimateur multilames
permettant une délimitation précise du champ d’irradiation, faisceau vertical (facilitant l’irradiation des
échantillons biologiques qui peuvent être posés sur une surface horizontale, évitant ainsi la mise au point de
montages complexes comme c’est le cas avec les faisceaux horizontaux) et, depuis cette année, aménagement, à
proximité de la salle d’irradiation, d’un laboratoire de radiobiologie (le CERCYL), sont autant d’atouts précieux
pour le développement de nos recherches au CRC.
Nos expériences actuelles se rapportent à l’induction de la mort cellulaire apoptotique par les neutrons
rapides, à l’analyse de ses mécanismes moléculaires et à sa modulation pharmacologique. Pour analyser les
mécanismes de l’apoptose, nous utilisons des cultures cellulaires présentant des radiosensibilités variées ainsi
que de nombreuses méthodes (western blotting, cytométrie en flux, tests de prolifération et de survie...). Elles
vont nous permettre de déterminer si les voies de déclenchement de l’apoptose sont identiques, ou différentes, de
celles empruntées par les radiations à TEL faible (rayons X et gamma). Pour ce faire, nous comparons l’apoptose
induite dans la lignée lymphoide humaine TK6, et dans deux de ses variants exprimant des anomalies dans
l’expression du gène suppresseur de tumeur p53, en l’occurence WTK1 (p53 muté) et NH32 (p53 KO). Nos
résultats nous ont dores et déjà permis de mettre en évidence le rôle central de la protéine mitochondriale BID
dans le déclenchement de l’apoptose dans ces cellules par les neutrons rapides (Fischer et al, BBRC, 2003).
Un autre volet de nos expériences au CRC est consacré à la modulation de l’apoptose par des agents
utilisés en chimiothérapie (principalement le cisplatine) et par des composés présentant une activité cytotoxique
susceptible de renforcer l’effet des neutrons rapides : dérivés du resvératrol, composés organoruthénés, etc. Les
cellules sont des RDM4 (lymphome murin), des OE-21 (carcinome oesophagien squameux d’origine humaine)
et des U-87 (glioblastome humain). Nous avons montré que le cisplatine, à des concentrations subtoxiques, était
capable de renforcer de façon importante la cytotoxicité des neutrons rapides (Fischer et al, 2003, soumis). A
terme, ces résultats pourront conduire à des applications en radiothérapie, notamment dans la définition de
45
nouveaux protocoles chimio-radiothérapeutiques. Toujours dans le domaine de la modulation pharmacologique
de l’apoptose induite par les neutrons rapides, nous évaluons également le potentiel radioprotecteur d’un
composé polyphénolique, la norbadione. Les cellules sont ici des lymphocytes de souris, extrêmement
radiosensibles, et qui constituent de ce fait de précieux modèles. Vis-à-vis d’une irradiation par des neutrons
rapides, la norbadione prévient l’apoptose induite par ces particules, et possède donc une activité radioprotectrice
marquée, susceptible d’être mise à profit en radioprotection.
Durant ces 12 derniers mois, nous avons pu bénéficier de 10 shifts, ce qui nous a permis de poursuivre
les investigations en cours et d’en entreprendre de nouvelles. Menées par deux doctorants de notre laboratoire,
les expériences réalisées au cyclotron de Louvain-la-Neuve constituent une partie importante de leur travail de
thèse et révêtent de ce fait une importance capitale pour l’aboutissement de celui-ci. Aussi, au vu des nombreux
résultats obtenus, nous comptons en 2004 développer encore d’avantage ce programme de recherche centré sur
l’induction de l’apoptose par les neutrons rapides.
46
7. ACCÉLÉRATEUR VAN DE GRAAFF / VAN DE GRAAFF ACCELERATOR
7.1. Elemental analysis of light constituents in thin plastic films
Y. El Masri, Ch. Heitz, C. Dufauquez and J. Van Mol (FNRS and Institut de Physique Nucléaire, Université
catholique de Louvain, Louvain-la-Neuve, Belgium)
Résumé : Cette année nos travaux ont porté essentiellement sur la mise au point d’une méthode permettant
l’analyse élémentaire par la technique nucléaire RBS (Rutherford Back-Scattering) de films en
plastique contenant des éléments légers outre l’hydrogène, le carbone et l’oxygène. Le but est de
développer une méthode rapide permettant la détection et l’identification de matières dangereuses
telles que : les drogues, les explosifs et les matériaux toxiques qui contiennent essentiellement des
éléments tels que : l’hydrogène, le carbone, l’azote, l’oxygène et selon les cas, du fluor, du soufre ou
du chlore.
7.1.1. Introduction
The use of toxic chemicals and of plastic explosives by terrorists necessitates the development of rapid
and efficient analytical methods in order to detect and identify the threat materials. Among the available
methods, Rutherford Back-Scattering (RBS) nuclear technique presents interesting possibilities because these
materials contain mainly hydrocarbons with additive atoms such as Fluorine, Sulphur or Chlorine either under a
toxic or explosive combination. Thus, the elements entering the molecular composition of these products are
mainly elements with Z < 20 for which the mass resolution in RBS analysis is optimal.
To test the possibilities of this nuclear technique in such a field, commercially available plastic films
have been irradiated under various conditions, both with He (alpha) and proton beams. The plastics used for
these experiments were the following polymers :
Mylar (C10 H8 O4)n ; Kapton (C22 H10 N2 O4)n ;Polyethersulfone, PES (C12 H8 S O3)n ; Polypropylene (C3
H6)n ; Polyvynilidène chloride, PVDC (C2 H2 Cl2)n and Teflon (C2 F4)n.
7.1.2. Analysis with a 1 MeV He beam
Under the applied experimental conditions (beam intensity of several nA, irradiation time of about one
hour) the plastic foils have not resisted immediate irradiation. As a consequence, a 100 Å thick copper layer was
evaporated on one face of the targets. The targets were than analysed on both faces. As an example, Figure 1
displays two spectra obtained from a PES film : when the beam impinges on the side of the copper layer a peak
corresponding to this element appears, together with the plateaus corresponding to S, O and C constituents. (The
peak appearing at lower energies than the C related structure results from the electronic and the detector
associated noise ). The copper peak is absent when the beam impinges on the other face (PES) of the target.
This effect, together with the plateaus corresponding to S, O and C, indicates that the target has to be considered
as “thick” for this beam energy (the nominal thickness of the target is 25 µm).
47
Figure 1 : Spectra of 1 MeV He particles scattered by a 25 µm polyethersulfone (PES) foil
with a 100 Å copper layer on one face.
a) beam impinging on the copper layer ; b) beam impinging on PES.
The relative atomic concentrations, as estimated using the SIMNRA computer code, show strong
disagreements with the expected “theoretical” values deduced from the chemical formulas given by the industrial
manufacturer, excepted for the PES-Cu sample. The general trend is the observed strong increase of the carbon
concentration which we may attribute to the destruction of the polymer by the beam impact leaving a carbon
enriched frame. Carbon deposition by the beam or the oil of the vacuum pumping systems may also contribute
to the same effect. The detailed elemental concentrations determined for PES-Cu target are given in Table 1.
Atomic concentrations
C
H
O
S
PES (C12 H8 O3 S)n
0.500
0.333
0.125
0.042
Cu/PES
0.520
0.333
0.100
0.047
PES/Cu
0.550
0.328
0.080
0.042
Table 1 : Atomic concentrations of C, H, O and S in PES plastic film as estimated through the
SIMNRA code : PES : expected “theoretical” values ; Cu/PES : case of the alpha
beam impinging on the copper face ; PES/Cu : Beam impinging on the PES face.
Consequently, we deduce from these experiments that the use of He projectiles is not well suitable for
the present purpose :
-
immediate irradiations would result in the prompt destruction of the targets.
-
the evaporation of a metallic layer on the target surfaces necessitates a supplementary procedure and mainly
does not yield unambiguous results.
For these reasons, tests were performed with proton beams.
48
7.1.3. Analysis with 2.2 to 3.2 MeV proton beam energies
To reduce the target beam radiation damage, an alternative method consisted in using a proton beam
RBS method. However in this case, the expected elemental mass resolution is less favourable than for He
projectiles with comparable incident energies. A mean to compensate this effect is the increase of the proton
energies. For this reason, tests with protons of energies ranging between 2.2 and 3.2 MeV were performed. In
Figures 2, 3 and 4 the spectra obtained for Mylar, PVDC and PES targets are displayed. They show that, for
protons with energies above 3 MeV, quite satisfactory results are obtained for the three analysed polymers.
Figure 2 : Spectra of 2.2 and 3.2 MeV protons scattered by a 3.5 µm mylar foil.
Figure 3 : Spectra of 2.2 and 3.2 MeV protons scattered by a 12.5 µm polyvinylidene
chloride foil.
49
Figure 4 : Spectra of 2.2 and 3.2 MeV protons scattered by a 25 µm polyethersulfone (PES)
foil.
In the case of PES the quantitative analysis, through the SIMNRA code, yields the concentrations listed
in Table 2.
Beam energy
PES (C12 H8 O2 S)n
Atomic concentrations
(MeV)
C
H
O
S
Expected
0.500
0.333
0.125
0.042
2.2
0.599
0.282
0.113
0.006
3.0
0.609
0.292
0.093
0.006
3.2
0.569
0.326
0.100
0.005
Table 2 : Atomic concentrations of C, H, O and S elements in the PES target as “expected” and estimated
by the SIMNRA code for various energies of the proton beam.
As it appears in Table 2, the carbon ratio is in all cases higher than the expected value probably due to
the same reasons as mentioned previously. The most striking experimentally observed discrepancy concerns the
elemental concentrations of sulfur. They appear lower by nearly a factor ten as compared to the nominal or
“expected” values. This may result from radiation effects induced by the beam leading to the production of
volatile sulphur compounds such as SH2 or SO2. However, it is also possible that the sulphur concentration of
the industrial polymer is not the one corresponding to the “theoretical” chemical formula given by the
manufacturer. This appears in the spectra of Figure 5 corresponding to the analysis of a 25 µm Teflon film with
a 3.2 MeV proton beam. The elements N, O and Al are normally not present in Teflon chemical formula (C2F4)n
, nor brought by the beam. In the present case, their presence must only result from the industrial synthesis of
this film. The very high concentration of C suggests that other hydrocarbons are present in the film. The
surprising presence of Al may be related to fluorine.
50
Figure 5 : SIMNRA fitted spectrum of 3.2 MeV protons scattered by a 25 µm Teflon( C2F4)n
foil. Estimated atomic concentrations : C 0.801, F 0.067, N 0.078, O 0.050,
Al 0.003.
7.1.4. Conclusions
These experiments show that protons with energies higher than 3 MeV can successfully be used for the
RBS elemental analysis of light elements in plastic films with a good sensitivity and a good mass resolution.
Technical progress has still to be done in the field of the counting rates supported by our electronics in order to
reduce the irradiation time of the samples and consequently to increase the accuracy of the determination of their
elemental composition. Concerning the RBS analysis with protons it would probably also be needed to
experimentally reinvestigate some cross section values for specific nuclear resonant reactions.
51
8. RECHERCHES MENEES PAR LE CENTRE DES RADIATIONS SPATIALES
(CSR) / RESEARCHES AT THE CENTER FOR SPACE RADIATIONS (CSR)
Résumé : Le Centre des Radiations Spatiales (CSR) conduit des recherches sur les radiations de
l’environnement de la Terre (leur type, leur flux, leur variation spatio-temporelle,…) ainsi que leurs
effets sur les organismes et équipements évoluant dans cet environnement. Dans le cadre de ses
différents projets le CSR a poursuivi l’analyse des données des missions OERSTED, CLUSTER et
IMAGE. Les données du CPD à bord d’OERSTED ont été distribuées en vue de leur utilisation dans
la modélisation des ceintures de radiation. Les données de l’expérience WHISPER sont analysées en
vue de la cartographie d’ondes VLF et ELF spatiales. Deux méthodes pour mesurer la vitesses de
rotation de la plasmasphère terrestre sont en train d’être explorées. Ces méthodes analysent les
clichés pris par la caméra EUV du satellite IMAGE. Ces travaux se font en collaboration avec des
membres de l’unité de physique mathématique de l’UCL et de l’Institut d’Aéronomie Spatiale de
Belgique.
8.1. Radiation environment research with multiple monitors
M. Cyamukungu, Gh. Grégoire, D. Heynderickx (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium and Institut d'Aéronomie Spatiale de Belgique, IASB)
The RERMM project is a response of an ESA funded consortium lead by ONERA, to the questions
raised by inaccuracies or incorrectness of the commonly used space radiation models like AP8 or AE8. As can
be seen in the Fig. 1, the flux of high energy protons obtained from the Oersted mission is somewhere an order
of magnitude higher than the AP8 predictions.
Figure 1 :
Comparison between proton fluxes (E > 60 MeV) measured by the Oersted/CPD (black) and AP8MAX predictions (blue) along the Oersted orbit.
The CSR is responsible of Oersted/CPD data analysis within the RERMM project. It has released its
contractual Technical Note in June 2003. The Oersted data along with results from PROBA, XMM, SAC-C
missions will be used to consolidate the Salammbo code developed at ONERA, Toulouse.
52
8.2. Classification of sources of single event effects in space
M. Cyamukungu, G. Degreef, S. Benck, Gh. Grégoire (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium et Institut d'Aéronomie Spatiale de Belgique, IASB)
One of the objectives of the Center for Space Radiations is to characterise hazardous radiation to
electronic devices of given specifications. This task includes the assessment of the most relevant ionising
radiation that may induce SEE, specifically Single Event Upset (SEU) into very sensitive devices. The tool
evaluation phase has been completed in 2003: it manly comprises a comparison between evaluated cross sections
of the p + Si reaction and results from physics contents of the GEANT4 QGSP-BIC physics list.
Cross section (mb)
Reaction
GEANT4
Table 1 :
ICRU63 [1]
Si(p,p)X
963
951
Si(p,d)X
15
68
Si(p,t)X
2
8
Si(p,α)X
138
144
Proton, deuteron, triton and alpha-particle production cross sections
for an incident proton energy of 100 MeV on Silicon. Comparison
between Geant4 calculations and evaluated values indicated in the
ICRU63 Report[1].
To perform this study, a nuclear reaction experimental setup has been modelled for GEANT4.
Simulation of a cross section measurement was performed and cross section values for several channels were
obtained after the event counting and analysis phase. The Table 1 shows some preliminary results of this work.
Nuclear reactions of protons on silicon produce light ions of mass ranging from proton to α-particles and heavy
ions from carbon to silicon. Primary heavy ions have been considered as stopped by satellite shielding and do not
interact with electronic components inside satellites. On the other hand, the energy deposited by light ions in
electronic components is considered to be far lower than the SEU threshold energy. However, the continuously
increasing sensitivity of devices may lead to SEU production by direct ionisation by the heaviest light ions (He)
and the lightest heavy ions (C, N, O, F). This explains the interest of the CSR to models of He (E > 40 MeV/n)
and C, N, O and F (E > 100 MeV/n), all nuclei that may penetrate equivalent of 2 g/cm2 aluminium shielding.
The Energetic Particle Telescope (EPT) will be used in part to measure the flux of these ions.
The number of secondary ions produced by proton nuclear reaction must be compared to the flux of
primary ions in space in order to accurately determine the sources of SEU in sensitive electronic devices.
GEANT4 validation for other relevant interactions (C, N, O, F production) is underway.
[1] "Nuclear Data for Neutron and Proton Radiotherapy and for Radiation Protection", International Commission
on Radiation Units and Measurements ICRU , Report 63, 2000.
8.3. Measurement of angular velocity using EUV images of the earth’s
plasmasphere
J. Cabrera, J. Lemaire, F. Darrouzet (Institut d'Aéronomie Spatiale de Belgique, IASB); L. Jaques, J.-P. Antoine
(Unité de physique mathématique de l’UCL, FYMA); S. Guissot (Observatoire Royal de Belgique)
The goal of this work is to determine if some regions of the plasmasphere has a convection velocity
different of that of the Earth’s co-rotation. We are analysing the 140x150 pixels images of the plasmasphere
(figure 1) observed at 30.4nm, every 10min, by the EUV[3] camera onboard the IMAGE sattelite[4]. Two different
53
image analysis are checked. The first techniques uses Gabor-wavelet and Mallat-wavelet transformations [1]. The
second technique uses Lucas-Kanade’s algorithm [2].
Figure1 :
Example of an image from EUV camera. Somme different structures of the
plasmasphere as the limit (plasmapause), a shoulder, a channel or a plume are
illustrated in this figure. The earth is enclosed by a circle.
[1] Laurenz Wiskott. Pattern Recognition, 32(10):1751-1766 (1999).
[2] B. D. Lucas, T. Kanade. Proceedings of Imaging Understanding Workshop, pp. 121-130 (1981).
[3] http://euv.lpl.arizona.edu/euv.
[4] http://image.gsfc.nasa.gov.
8.4. VLF wave analysis from the observations of the WHISPER instrument
S. Benck, J. Lemaire, F. Darrouzet (Institut d'Aéronomie Spatiale de Belgique, IASB)
The Cluster programme is designed to study the small-scale spatial and temporal characteristics of the
Earth's magnetosperic plasma and the near-earth solar wind. The mission consists of 4 identical spacecrafts,
which enable physical measurements in three dimensions. The Waves of High frequency and Sounder for
Probing of Electron density by Relaxation (WHISPER) experiment, an element of the Wave Experiment
Consortium (WEC), is part of the many experiments onboard the Cluster spacecrafts. The Whisper instrument
yields two data sets: (i) the electron density determined via the relaxation sounder, and (ii) the spectrum of
natural plasma emissions in the frequency band 2-80kHz [1,2].
This year's activity was dedicated to adapt the WHISPER data processing software to run on LINUX
environment compiled by the installed Nagware Fortran 95 and Gnu C compiler. Data anlysis will now
concentrate around a special event in space namely the magnetic storm on 6th November, 2001. One of the aims
of this work is to find a relationship between VLF emission and other space weather parameters like the solar
wind speed, Dst index, Sym-H, Bz,... Special attention will be paid to the connection to electron flux
measurements from the Russian CORONAS-F mission.
Important output from the main WHISPER software package are the dynamic spectrogram, displaying
the E-field power as a function of time and frequency (central pannel of Figure 1). Figure 1 gives a sample of
comparison between wave activity and the Sym-H (symmetric disturbance field in the horizontal dipole pole
direction) evolution [3].
54
S Y M -H ( n T )
50 0
30 0
10 0
- 10 0
- 30 0
- 50 0
0
50
10 0
U T (m i n )
1 50
2 00
06 /1 1/2 00 1
Figure 1 : Frequency/time spectrogram (central panel) obtained during the mission while the spacecraft 1
is in the plasma sheet of the magnetosphere. The upper pannel shows the electric field power
(blue line), calculated from the frequency bins amplitudes integrated over the displayed
spectrum, compared to the full bandwidth integrated signal Epow (black line). The second pannel
indicates in white, periods when WHISPER is in standby. The lower pannel indicates for the
same period the Sym-H index as a function of time (blue line). The red vertical line suggests the
start of the magnetic storm, characterized by an important decrease of the Sym-H index together
with an increase of wave activity.
[1] P. M. E. Décréau et al., Space Sci. Rev. 79, p93-105, 1997.
[2] F. Darrouzet, P. Décréau, J. Lemaire, Physicalia Mag. 24, p3-16, 2002.
[3] WDC for Geomagnetism, Kyoto Dst index serviceat http://swdcdb.kugi.kyoto-u.ac.jp.
8.5. Construction of the Energetic Particle Telescope (EPT)
S. Benck, M. Cyamukungu, Gh. Grégoire, J. Lemaire (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium and Institut d'Aéronomie Spatiale de Belgique, IASB)
Résumé : Le Centre des Radiations Spatiales (CSR) conduit des recherches sur les radiations de
l’environnement de la terre ainsi que leurs effets sur les organismes et équipements évoluant dans cet
environnement. Dans le cadre de ses différents projets le CSR a poursuivi le développement d’un
instrument de mesure de radiations: le Télescope pour Particule Energétique (EPT). Ce dernier se
subdivise en deux parties adaptées aux particules de basse et de haute énergie respectivement. La
partie de basse énergie est constituée de deux détecteurs au silicium fonctionnant en ∆E-E et pour la
partie haute énergie, le plus épais des détecteurs Si est utilisé comme ∆E et l'énergie totale est
déterminée par une mesure digitale venant d'une succession de scintillateurs plastiques et
d'absorbeurs. La construction mécanique de l'EPT est dans sa phase finale.
The EPT will measure the high-energy particle fluxes with very good energy, angular and mass
resolutions. It measures the energy deposited by charged particles into twelve sensitive elements and processes
55
the information to identify the particles (0.2-10 MeV electrons, 4-100 MeV H and 16-400 MeV He ions) and to
determine their energy spectra and angular distribution.
The EPT consists of two "particle telescopes" placed in series separately adapted to low and high energy
ranges. The low-energy section consists of two silicon detectors. The high energy section is a so-called "range
telescope” in which the thicker silicon detector is used as a (∆E) sensor and a stack of absorbers and scintillatorbased detectors produce a digital measurement of the total energy (E). Figure 1 shows the mechanical supports
containing the two silicon detectors and the successive plastic scintillators with their absorbers as well as one of
the 4 light guides.
Figure 1 : View of the EPT detector with its collimator, lower energy and higher energy
detection sections and a light guide.
The EPT overall dimensions (collimator, detection sections, light guides, photomultiplier and printed
circuit included) are 205 mm x 205 mm x 190 mm. Its weight is about 7 kg, with the electronic readout included.
The power consumption is lower than 6 Watts. The radius of the EPT circular aperture was set to a diameter of
35 mm. The resulting maximum field of view angle is 50°.
Due to the widely varying fluences of electrons, protons and heavy ions within the radiation belts, it was
found necessary to provide this instrument with a stunning in-flight particle discrimination capability. This is
achieved by performing a thorough characterisation of the EPT by an intensive Monte-Carlo simulation using
GEANT4 software. With this optimised design procedure we intend to get background-free counting, even in the
channels devoted to particles of very low abundance in space.
This year’s activity was mainly concerned with the mechanical construction of the detector, including
the final design phase. An important challenge was to design a system that allows to connect the optical fiber
outputs of the scintillators to a 4 x 4 matrix channel photomultiplier (18 x 18 mm2 active area). In fact 10
successive circular scintillators constitute the sensitive devices, and they are surrounded by 6 anticoincidence
scintillation rings giving 16 light output spots distributed over a surface of 80 x 20 mm2 in the top plane and side
plane. The idea was to construct a light guide by moulding so that the 16 optical fibers are congealed in a rigid
structure. The left pannel of figure 2 shows the closed moulding box and the right pannel shows the finished
light guide before polishing of the extremity surfaces. The form of the light guide is determined by the minimum
space available (4 light guides, 2 for the high energy section and 2 for the "active" collimator) and by its weight.
The moulding material is a special araldithe.
56
Figure 2 : The left panel shows the closed moulding box and the right pannel shows the
finished light guide before polishing of the extremity surfaces.
In the near future it is planned to finish the technical layouts of the EPT modules and to go into the final
construction of the complete detector. The development of the electronic readout and signal analysis system
(printed circuit board) is at its first design stage and a test board will be achieved within the next year. We plan
to achieve preliminary tests of the whole by the end of next year.
57
II. RECHERCHES AUPRÈS D’AUTRES ACCÉLÉRATEURS
1. CHORUS : Production de particules charmées induites par des
neutrinos νµ
Th. Delbar, D. Favart, Gh. Grégoire, S. Kalinin, I. Makhlioueva (Institut de Physique Nucléaire, Université
catholique de Louvain, Louvain-la-Neuve, Belgium) et collaboration CHORUS
L'année 2003 a été principalement consacrée à la simulation des événements CHORUS avec courant
chargé. Les nouveaux critères pour la sélection des événements chargés ainsi que le petit désaccord sur le rapport
entre nombre d'événements charmés et nombre d'événements chargés ont montré la nécessité d'un nouvel outil
de simulation. Cet outil ne concerne que les données des émulsions obtenues par la procédure NETSCAN. A part
cela, notre ancien programme a été utilisé pour estimer les efficacités de sélection des événements charmés en
fonction de divers paramètres, tels que la distance parcourue (longueur de vol), multiplicités, moment linéaire
des muons primaires, etc...
Pour vérifier la pureté de l'échantillon obtenu d'événements charmés, deux tests indépendants ont été
réalisés. D'abord, la pureté a été vérifiée sur un échantillon d'événements simulés par Monte Carlo. Dans le
deuxième test, la qualité des événements sélectionnés a été vérifiée manuellement dans le laboratoire de
scanning de Nagoya: en conclusion, les deux échantillons sont en très bon accord.
Nous avons reçu un nouveau générateur de la collaboration NuTev qui nous permettra d'étendre nos
analyses à plus basse énergie. D'autre part, il a été possible de séparer les événements où le quark entrant en
interaction avec le neutrino est de type s de ceux où le quark est de type d.
2. CMS
S. Assouak, E. Burton (FNRS), J. de Favereau (FRIA), G. de Hemptinne (FRIA), C. Delaere (FNRS), Th.
Delbar, D. Favart, E. Forton, J. Govaerts, Gh. Grégoire, Th. Keutgen, G. Leibenguth, V. Lemaître (FNRS-UCL),
O.Militaru, A. Ninane, K. Piotrzkowski, X. Rouby, O. van der Aa (FRIA) (Institut de Physique Nucléaire,
Université catholique de Louvain, Louvain-la-Neuve, Belgium)
2.1. Activités liées à la construction du tracker "avant"
Le groupe CMS-Louvain a été actif dans les domaines suivants:
1. Qualification des senseurs au silicium et sensibilité aux dégâts radiatifs
2. Conception des circuits de refroidissement des pétales
3. Construction de groupes froids
4. Tests de circuits hybrides
5. Tests ("burn-in") des modules et des pétales
Pendant l'année 2003, le groupe CMS-Louvain a poursuivi intensivement la qualification des senseurs
au silicium et leur sensibilité aux dégâts radiatifs. Les essais mécaniques et thermiques sur plusieurs prototypes
de pétale ont eu lieu et les connecteurs d'entrée/sortie de fluide caloporteur sont entièrement définis. La
conception finale des circuits de refroidissement est bien avancée (point 2). Les dispositifs de tests des circuits
hybrides ont été construits, réceptionnés et présentés aux entreprises chargées de la fabrication (point 4). Les
tests simultanés de plusieurs des modules fonctionne correctement avec les versions les plus récentes des
logiciels de contrôle (point 5). La boite froide pour les essais de pétale est en phase finale d'assemblage (point 6).
58
2.1.1. Qualification des senseurs au silicium et sensibilité aux dégâts radiatifs
S. Assouak, E. Forton, Gh. Grégoire (Institut de Physique Nucléaire, Université catholique de Louvain, Louvainla-Neuve, Belgium)
Abstract : This year, the CMS sensor group has entered the full production phase. In this context, irradiations
for radiation tolerance test of the Si-microstrip sensors have been pursued at higher rates, raising the
need for more efficient use of the irradiation beam time and faster electrical tests. We therefore
doubled the irradiation capabilities using a bigger cold box in the T2 beam area (allowing us to
replace with a new batch the sensors being irradiated without opening the irradiation zone). Also,
about the electrical test set-up, we recently implemented a new probe needle moving with the chuck to
speed up tests. In parallel to the usual tests, an extensive cross-calibration with the Karlsruhe setup
has been carried out and some specific studies on radiation-induced evolution of CMS sensors helped
the group to take decisions on acceptance or rejection of Hamamatsu batches.
Les activités de tests de résistance aux radiations des senseurs silicium destinés au trajectographe de
CMS ont été poursuivies cette année. Le groupe senseur est maintenant en phase de production et les livraisons
hebdomadaires de détecteurs devraient se poursuivre jusque mi 2004. Cette année, nous sommes donc aussi
entrés en routine de test, et nous avons maintenu mais aussi modifié les outils précédemment développés pour
assurer une plus grande productivité. Ainsi, la capacité du dispositif d’irradiation a été multipliée par deux, et les
tests réalisés avec la station à micro-pointes ont été optimisés. Par ailleurs, nous avons affiné notre
compréhension des mesures et réalisé la dernière phase de calibration du dispositif avec celui de Karlsruhe (en
charge des mêmes tests de résistance aux radiations, réalisés cette fois avec un faisceau de protons). L’utilisation
intensive de ce dernier dispositif a aussi permis de détecter et corriger les derniers problèmes logiciels.
En parallèle avec les irradiations de senseurs et « demi-lunes » pour les tests routiniers, nous avons
réalisé certaines études plus spécifiques pour notre groupe. Notre expérience avec le faisceau de neutrons en
zone d'irradiation T2 nous a par ailleurs amené à apporter notre aide à divers groupes en visite à Louvain-laNeuve pour réaliser des tests de résistance aux neutrons.
En marge des tests dédiés à CMS, nous avons aussi procédé à l’irradiation de diodes à l’aide du faisceau
monocinétique de neutrons (voie Q). Ces diodes nous ont été fournies par un groupe de l’université de
Hambourg et devraient nous permettre, malgré la faible intensité du faisceau, de déduire de manière
expérimentale les facteurs « NIEL » pour des neutrons dont l’énergie excède 20 MeV. Les facteurs de
conversion fluence-dégâts subis par les senseurs Si n’ont en effet pour l’instant été déduits expérimentalement
que pour des énergies inférieures à 20 MeV: pour l'instant la communauté scientifique se base sur des
simulations numériques pour la majeure partie du spectre. Les résultats de ces tests sont en cours d'analyse.
2.1.1.1. Modifications du dispositif d’irradiation
E. Forton (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
Pour faire face aux arrivages fréquents de senseurs en provenance de Semiconductor Technology (ST)
et de Hamamatsu (HPK), et en vue de mieux rentabiliser le temps faisceau qui nous est alloué, une nouvelle
boîte de réfrigération a été installée en zone T2.
Cette dernière boîte (Figure 1), posée sur des rails, est prévue pour accueillir trois piles de senseurs. Ces
piles sont mises à tour de rôle dans l'axe du faisceau en déplaçant à distance le dispositif tout entier au moyen de
câbles d'acier traversant le blindage de la zone d'irradiation. Ce système permet d’irradier séquentiellement trois
jeux de senseurs sans intervenir dans la zone d’irradiation: nous évitons ainsi les temps d’attente dus au débit de
dose important immédiatement après l'arrêt du faisceau.
La polarisation des détecteurs en cours d’irradiation se fait au moyen des mêmes alimentations que
précédemment, auxquelles un dispositif de commutation a été ajouté pour permettre la polarisation successive
des différents jeux de senseurs.
L’irradiation requise pour atteindre une fluence moyenne de 0,8 1014 neutrons/cm dure environ 5 h pour
les senseurs ST de 500 µm d’épaisseur. Il faut environ 17 heures pour atteindre les 2.4 1014 n/cm2 imposés par
les senseurs HPK de 320 µm d’épaisseur, il nous est désormais possible d’irradier un jeu de chaque fabricant en
24 h, temps généralement alloué aux irradiations pour CMS (et comprenant la mise au point du faisceau).
59
Figure 1 : Nouvelle boîte installée en zone d'irradiation montrant les trois orifices possibles
pour l'irradiation par le faisceau de neutrons, indiqué par la ligne rouge.
2.1.1.2. Mise à jour des tests électriques des senseurs et intercalibration avec Karlsruhe
S. Assouak, E. Forton (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve,
Belgium)
A la suite du problème de "pinholes" créés par notre dispositif de mesure l’an passé (cf. rapport annuel
CYCLONE 2002), nous avons approfondi l’intercalibration des dispositifs installés ici à Louvain-la-Neuve et à
Karlsruhe. Ces tests comparatifs des mesures ont été présentés lors de réunions du groupe senseur.
a) Résistances de polarisation
Après irradiation, et pour les senseurs de pleine taille, nous avions encore des problèmes de mesure des
résistances de polarisation. Ces mesures étaient en effet perturbées par le courant de fuite important que
présentent les senseurs une fois qu’ils ont été soumis à une dose équivalente à 10 ans de fonctionnement au
LHC. Ces problèmes ont été résolus en adaptant le circuit de mesure des résistances. La mesure du courant
passant par la résistance est maintenant effectuée sur le contact DC ("DC pad"), et n’est donc plus perturbée que
par le courant de fuite d’une unique piste, et non par celui du détecteur tout entier.
Avant les modifications
Après les modifications
W7 post-irra
OB1 post-irra
OB1 pre-irra
W7 pre-irra
12
Rpoly (MOHMS)
Rpoly (MOhms)
14
W1 post-irrad
W4 post-irra
W4 pre-irra
W1 pre-irra
3
10
8
6
4
2,5
2
1,5
1
0,5
2
0
0
0
5
Strip Order
10
0
15
5
10
Strip Order
Figure 2 : Résistance de polarisation avant et après les modifications. Mesures obtenues
après irradiation aux neutrons.
60
15
Electrometer
Keithley +
6514
Strip DC-pad
-
Low Voltage
Test-structure
+
Agilent 6614C
-
Bias ring
Sourcemeter
-
Keithley
2410
Backplane
+
Switch Unit
Agilent
34970A
Temperature of the chuck(Pt100)
Humidity
Figure 3 : Schéma de mesure de la résistance de polarisation à la suite des modifications des circuits de mesure.
b) Résistances interstrip
Tout comme dans le cas des capacités interstrip (voir ci-après), la forme de la courbe représentant la
valeur d’une résistance interstrip en fonction de la tension de polarisation présentait un comportement correct,
mais il subsistait un problème à propos des valeurs absolues de la résistance, beaucoup trop basses (Figures 4 et
5).
Une modification du circuit de masse du blindage des câbles a permis de limiter les perturbations de la
mesure du courant. Les valeurs mesurées sont maintenant compatibles avec celles obtenues à Karlsruhe.
Figures 4 et 5 : Différence entre les résistance de polarisation mesurées à Karlsruhe et
Louvain pour une structure irradiée avec des protons. Les mesures obtenues
pas Louvain étaient beaucoup plus basses
61
c) Capacités interstrip
Figures 6 et 7 : Comparaison des valeurs de capacité interstrip obtenues à Karlsruhe (à gauche) et Louvain-laNeuve (à droite) avant les modifications du dispositif de mesure.
D’un autre côté, l’analyse des mesures de capacités interstrip,présentaient une bonne concordance avec
les mesures réalisées en Allemagne (Figures 6 et 7) , et montre l’évolution de la valeur des capacités interstrip
(Cint) en fonction de la polarisation du senseur. Toutefois la comparaison des mesures réalisées sur des structures
de tests ou des senseurs de plaine taille présentaient des inconsistances difficilement explicables*, suggérant une
erreur au niveau du dispositif de mesure en lui-même. Des tests ont été réalisés sur un senseur artificiel
(« dummy sensor») qui simule les propriétés électriques des senseurs (résistances, capacités). Nous avons mis en
évidence que la mesure était perturbée par des connexions simultanées sur le contact AC (« AC-pad ») et sur
l’une des pistes lors de la mesure de la capacité interstrip. Ceci est dû à la faible impédance de couplage des
pistes aux fréquences élevées utilisées lors des mesure de la capacité interstrip (Figure 8). La mesure se passe
donc comme si l’aiguille située sur le contact AC était, elle aussi, connectée au contact DC.
controller
Backplane
AC pad 1
Multiplexer
DC pad 1
GPIB
H
LCR
Agilent L
DC pad 2
Bias ring
H
Shift
CV-box
H
L
L
1
H
keit2410
2
3
L
4
Keit6514
H
5
L
6
7
H
8
HP6614 L
Gnd
1
2
3
4
Guard ring
GPIB
Figure 8 : schéma de mesure des capacités interstrip.
couplage est représentée en jaune.
*
La faible impédance de la capacité de
Les valeurs obtenues pour des structures de test ou des senseurs de pleine taille étaient pratiquement identiques
alors que les pistes ont des longueurs très différentes.
62
Ce problème a été résolu en connectant cette aiguille au capacimètre au cours de la mesure de Cint.
Désormais, les courbes obtenues à Louvain se superposent à celles obtenues en Allemagne, et le rapport entre les
capacités mesurées sur un senseur et sur une structure est de 3.5, proche du rapport théorique de 3,9 (basé sur les
approximations usuelles de calcul des capacités, en négligeant les effets de bord).
Après les modifications
Avant les modifications
5,0
4,0
Full sensors
3,0
Cint(pF)
Cint(pF)
3,5
2,5
4,0
3,5
2,0
1,5
3,0
1,0
2,5
0,5
0,0
W1
W4
4,5
0
100
200
300
400
500
600
700
0
800
200
400
600
Voltage(V)
Voltage (V)
Figure 9 : Capacité interstrip avant et après les modifications. Mesures obtenues après une irradiation aux
neutrons.
d) Installation d’une aiguille mobile sur le chuck
Mis à part les quelques modifications apportées aux différents circuits de mesure et à la matrice de
connexion, nous avons récemment mis en place une aiguille fixée à la platine ("chuck"). Cette dernière se
déplaçant avec le senseur en cours de test, elle permet de maintenir la polarisation au cours des déplacements
nécessaires aux mesures sur les différentes pistes. L’avantage principal d’un tel dispositif est d’éviter la
multiplication des "rampes" de polarisation/dépolarisation. La figure 10 reprend une photographie du chuck ainsi
modifié.
Figure 10 : Aiguille fixe placée sur le chuck.
e) Résultats obtenus sur les structures de test pour CMS
Depuis le début de l’année 2003, plus de 150 structures ont été irradiées en zone T2 et analysées après
irradiation pour des tests de routine.
Un format de fichier standard reprenant les résultats obtenus en irradiation a été défini lors d’une
réunion du groupe senseur, organisée à Louvain-la-Neuve en mai 2003. Depuis, nos résultats sont désormais mis
63
à disposition des collaborateurs du groupe senseur au moyen d'une page Internet accessible sur le site du groupe.
Pour chaque ensemble (« set »), nous créons ainsi un fichier résumant les principaux résultats et reprenant les
figures les plus intéressantes. Les centres de tests responsables de la qualification des senseurs ont ainsi
directement accès aux données obtenues lors de nos irradiations.
f) Etude spécifique du modèle de Hambourg appliqué au cas des senseurs Hamamatsu
Le modèle développé il y a quelques années par le groupe de recherche sur les détecteurs à semiconducteur de l’université de Hambourg est celui communément utilisé pour prédire l’évolution des tensions de
déplétion et courants de fuite de détecteurs soumis à d’importantes doses de radiations. A ce titre, ce modèle est
aussi utilisé pour prédire le comportement des senseurs silicium à micropistes dans CMS au cours de 10 ans de
fonctionnement au LHC.
Le choix du type de senseur, et en particulier de la résistivité initiale du substrat de silicium, a été fait de
sorte à assurer une tension de déplétion limitée en fin de vie du détecteur. Un certain nombre de senseurs livrés
en ce début d’année par Hamamatsu présentaient de tensions de déplétion très faibles. Si ceci peut être un
avantage en début de vie des détecteurs (ils fonctionnent à plus basse tension), cela devient un problème par la
suite, puisque l’inversion du type de substrat viendra plus vite, et il en résultera une tension de déplétion plus
importante par la suite, dépassant potentiellement les seuils tolérés par les alimentations (limitant ainsi, par
recombinaison, l’efficacité de détection).
Depletion voltage vs. Fluence
4,E+02
4,E+02
Vdep/geom. Factor (V)
3,E+02
Hamburg Model (Vdep init= 50V)
Hamburg Model (Vdep init=110V)
W1tid
W3
IB1
3,E+02
2,E+02
2,E+02
1,E+02
5,E+01
0,E+00
0,0E+00
5,0E+13
1,0E+14
1,5E+14
2,0E+14
2,5E+14
3,0E+14
3,5E+14
Fluence (n/cm^2)
Figure 11 : Tensions de déplétion obtenues lors du test des senseurs de haute résistivité de
chez Hamamatsu. Les tensions sont normalisées à la géométrie des différents
détecteurs.
Une étude dédicacée à l’évolution des tensions de déplétions (Figure 11, où l’on voit aussi la
comparaison des résultats avec les prédictions du modèle de Hambourg réalisée en utilisant les paramètres
standards) pour ce jeu de senseurs (plus particulièrement soumis aux radiations puisque destinés à être placés
dans la partie interne du trajectographe) a donc été réalisée ici à Louvain. Il a été montré que seuls les senseurs
du type IB1, les plus proches du point d’interaction, devaient être rejetés sur base des résultats obtenus en
irradiation, compatibles avec le modèle de Hambourg.
Il est aussi important de mentionner que cette étude a permis d’affiner notre compréhension du modèle,
et aussi d’intégrer une estimation plus correcte des tensions de déplétion attendues après irradiation dans nos
fichiers de résultats (cf. paragraphe ci-dessus).
64
g) Etude des effets induits par les neutrons dans les senseurs CMS au moyen de la technique TCT
S. Assouak, Gh. Grégoire (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve
Belgium)
Récemment nous avons entrepris des mesures TCT(Transient Current Technique), à Karlsruhe en
Allemagne. Cette technique consiste en l’injection de paires (e+, e-) dans la diode P-N, constituant notre
détecteur, au moyen d’un pulse Laser (Diode laser de 670 nm) et voir l’évolution des ces porteurs de charges
tout au long de la jonction Ces mesures fournissent des informations sur leur mobilité, le profil du champs
électrique à l’intérieur du substrat, l’efficience de collection de charge, la concentration de la charge
d’espace…etc [1]. Nous avons utilisé deux diodes, dont une déjà irradiée, et mesuré le courant induit par le
mouvement des électrons(trous), à différentes tensions de polarisation du détecteur (déplétion progressive). Les
résultats préliminaires sont représentés sur les figures ci-dessous. A basse tension (déplétion partielle) le
phénomène de recombinaison est prédominant (voir figure 12), contrairement à ce que l’on observe à la
déplétion totale, où la décroissance du signal, est relativement lente au début, marquant le temps de dérive mis
par les porteurs injectés pour atteindre l’électrode correspondante. Pour la diode irradiée (fig. 13), l’on remarque
une décroissance plus rapide du signal, due à l’inversion du type de la jonction. Une analyse plus approfondie
des ces données est en cours. Un dispositif de mesure similaire est en train de se développer ici à Louvain-laNeuve avec plus de facilités telles que le contrôle de la température. Cela nous conduira également, à l’étude des
propriétés microscopiques des radiations, en utilisant des techniques appropriées telles que la TSC (Thermally
Stimulated Current) pour mieux comprendre les changements introduits dans la structure du semi-conducteur.
Not fully depleted
Fully depleted
Transient Curent (A.U)
0,5
Transient Curent (A.U)
30 V
0,4
0,3
0,2
0,1
0,0
-0,1
6,00E-008
0,8
140 V
0,6
0,4
0,2
0,0
-0,2
6,00E-008
8,00E-008
Time (s)
8,00E-008
Time (s)
Figure 12 : Transient Current vs Time before type inversion (no irradiated diode) before and after full
depletion.
Not fully depleted
Fully depleted
0,06
60 V
0,6
Transient current (A)
Transient Current (A)
0,7
0,5
0,4
0,3
0,2
0,1
0,0
-0,1
6,00E-008
8,00E-008
0,05
330 V
0,04
0,03
0,02
0,01
0,00
-0,01
1,00E-007
Time (s)
Time (s)
Figure 13 : Tansient Current After type inversion (irradiated diode) before and after full depletion.
[1] Z. Li et al. Nucl. Instr. And Methods in Physical Research A 388 (1997) 297-307.
65
2.1.2. Conception des circuits de refroidissement des pétales
Gh. Grégoire et atelier de mécanique UCL-FYNU (Institut de Physique Nucléaire, Université catholique de
Louvain, Louvain-la-Neuve, Belgium)
Abstract : Various prototypes of petals have been designed and construction to improve their mechanical and
thermal characteristics. A large effort has been done to ease their construction. In parallel, we have
designed and finalized the design of the titanium manifolds for the coolant. Their final assembly rests
on a laser-welding set-up, which has been constructed and is now operational.
Plusieurs prototypes de pétales ont été construits et les essais mécaniques et thermiques sont terminés.
Cette succession d'essais a pour but d'optimiser la construction tout en améliorant les caractéristiques
mécaniques (déformations lors de la mise en froid) et thermiques (diminution des gradients de température entre
le liquide réfrigérant et les senseurs). Simultanément l'ensemble du dispositif s'approche du modèle final de
pétale qui sera reproduit à environ 300 exemplaires. En ce qui concerne la contribution de Louvain, ces études
ont été faites tant pour les pétales de type "front" que pour les pétales de type "back".
Chaque prototype exige la fabrication de nombreux gabarits de cintrage, de positionnement des
échangeurs de chaleur et de collage. A ce sujet, nous avons développé et mis en œuvre une presse pneumatique
destinée aux opérations de collage (Figure 1). Elle permet de développer une poussée totale d'environ 8000 N.
Cela correspond à une pression de collage de l'ordre de 26 kPa pour un pétale "front" (surface de 3044 cm²).
Figure 1 : Presse pneumatique pour les opérations de collage des pétales.
D'autre part, des efforts importants ont été consacrés aux connecteurs spéciaux pour les entrées et sortie
du liquide réfrigérant. Les contraintes d'encombrement et de solidité sont extrêmement sévères. Plusieurs
prototypes en titane ont également été fabriqués pour converger en fin d'année vers un modèle satisfaisant.
La petite taille de ces connecteurs et leur rattachement aux tuyaux de titane à parois minces, situés dans
l'épaisseur des pétales, requiert leur micro-soudure par faisceau laser.
66
Dans ce contexte, un laser à impulsions Nd-YAG nous a été livré à la mi-2003. Il permet de fournir des
impulsions infrarouges (1065 nm) avec une puissance crête de l'ordre de 90 kW sur une tache focale de 60
microns.
La seconde moitié de l'année a été consacrée à la conception et à la construction d'un dispositif de
"manipulation" du faisceau laser. Cette table à quatre axes (trois de translation, un de rotation) est programmable
par un ordinateur industriel et permet de déplacer le point de focalisation du faisceau laser selon le tracé requis
avec une précision de l'ordre de 20 microns. L'installation est relativement complexe en raison des impératifs de
sécurité et de commande.
Figure 2 : Vue partielle du dispositif de soudure par faisceau laser. Le générateur laser est
visible à gauche (châssis bleu). Le faisceau laser est amené à la tête de soudure
(en noir à droite) par une fibre optique (câble rouge).
2.1.3. Construction de générateurs de liquide froid
Gh. Grégoire, D. Michotte et atelier de mécanique UCL-FYNU (Institut de Physique Nucléaire, Université
Abstract : In 2003, our group has constructed, tested and delivered five generators of cold fluid. Three
additional units are in the final stages of assembly and will be delivered to Hamburg, Karlsruhe and
Louvain in Spring 2004. A 2 kWatt special unit is under construction for the University of Lyon. It will
be used for the tests of the complete CMS Tracker end-caps.
La mise en oeuvre des essais thermiques nous a conduit à concevoir un groupe de refroidissement
performant, spécialement adapté aux éléments du trajectographe de CMS. Ce groupe est devenu le modèle
reconnu par CMS pour toutes les installations similaires de la collaboration. Les groupes sont entièrement
programmables par ordinateur pour être insérés dans les dispositifs d'acquisition des données de Lyon-CMS.
67
Figure 1 : Générateur de liquide froid (vu avec la chambre froide ouverte). Il développe une
puissance thermiques d'environ 500 Watts à -20°C.
Outre le prototype, notre laboratoire a déjà construit et livré cinq unités de refroidissement pour les
centres chargés de l'assemblage des pétales: Aachen 1 et Aachen 3, Bruxelles, Lyon, Strasbourg.
Trois générateurs supplémentaires sont à un stade avancés de construction pour être livrés au début
2004 aux universités de Hambourg, Karlsruhe et Louvain.
D'autre part, l'Institut de Physique Nucléaire de Lyon est chargé de l'assemblage et des essais des roues
du tracker CMS. Ce sont des grands ensembles qui peuvent totaliser quelques 150 pétales.
Les générateurs de liquide froid évoqués ci-dessus ne disposent pas d'une puissance thermique
suffisante. Nous avons développé un générateur qui permet d'atteindre environ 2000 Watts à -20°C. Sa
construction est aussi très avancée. La livraison à Lyon devrait intervenir à Pâques 2004.
2.1.4. Tests de circuits hybrides
L. Bonnet, V. Lemaître, X. Rouby (Institut de Physique Nucléaire, Université catholique de Louvain, Louvainla-Neuve, Belgium)
Résumé : Les développements matériels et logiciels concernant un testeur industriel – FHIT– de circuits
hybrides frontaux pour le trajectographe de CMS, commencés dès 2001, ont continué. Ils ont mené à
l'installation de plusieurs de ces dispositifs en industrie et dans divers laboratoires. Une version
allégée et portable – LFHIT – a également été conçue pour les laboratoires manipulant des structures
basées sur ces circuits hybrides et leur distribution a déjà commencé. La compatibilité avec la banque
de données des éléments du trajectographe de CMS a nécessité le développement d'un programme de
formatage des données provenant des tests de circuits hybrides pour la production industrielle.
A setup for quality control of CMS tracker front-end hybrids has been developed by our institute [1].
This industrial tester – FHIT (figure 1a) – has to test the hybrid within 100s, at three different stages: the
connectivity (search for broken- and open-lines, short circuits…), the electrical parameters (current
consumptions, I²C communications, …) and the functionalities (pedestal, noise, gain, …). In order to meet these
specifications, a dedicated front-end has been developed by our institute, which is connected to a digitalization
68
board – ARC – coming from RWTH Aachen III. The front-end is based on a switch matrix connected to the
output connector of the hybrid, which allows the implementation of both the connectivity and electrical tests.
Once these tests are done, the data itself, which consist in output signals coming from the hybrid when it gets
trigger sequences, is digitalized by the ARC board internal ADCs. There, quantities like noise or gain are tested
against criteria defined by the CMS collaboration. The implementation of these criteria in based on the ARC
software code [2].
Figure 1a : Dual-FHIT setup with 2 hybrids.
Figure 1b : Mechanical structures
A user-interface is available for the automatization of tasks [3]. This software – FHITS (figure 2) – has
been written with NI LabVIEW. It deals with the communication between the computer and the FHIT, whatever
its kind (mono- or dual-FHIT), the power supply (for remote control) and the barcode scanner (for hybrid
identification). It manages the sequence of subtests, the errors that occur with hybrid problems and creates an
ASCII output file for every hybrid test. This output file contains the data needed for the hybrid characterization
and feeds the CMS tracker database. As the FHIT setup had to be used at CERN, in the industry – HybridSA –
and in IReS Strasbourg before the database tables were defined, the availability of FHITS and the production of
database compatible files has been factorized. This means that a converter – XML parser – was needed to create,
from the ASCII output of FHITS, the XML files which will be uploaded into the database (cf §1.2).
Figure 2 : FHITS monitor display.
Some statistics on current consumption, pedestal, noise (figure 3) and gain were gathered for the frontend hybrid characterization from the data produced by FHIT setups. These were the first characterization data
available for hybrids. In particular, this data highlighted an unknown feature of some hybrid components – the
dependance on trigger frequency of APV current consumption.
69
Figure 3 : Examples of characterization data from FHIT measurements. a) Left: noise
distribution per APV Channel for a given APV address. b) Right: mean
distribution of noise per APV address [1].
As the specification of tests evolved, some mechanical structures have been developed to host hybrids
for a particular electrical subtest, needed only in the industry (figure 1b).
All these hardware and software aspects have been developed since 2001, in strong collaboration with
RWTH in Aachen, IReS in Strasbourg and CERN. Several setups have been distributed in these centers and are
used to test hybrids for the production in the industry, for the reception at CERN and for the quality and
insurance in Strasbourg.
2.1.4.1. A portable tester LFHIT for the CMS hybrids
L. Bonnet (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
A light and portable version of the setup has been developed. It works without any user-interface but a
simple hyperterminal and a direct connection to a computer, via either serial or USB port. It needs no external
power supply. It is meant to test quickly (~ 20s) connectivity and electrical parameters, but no functionality, of
hybrids or hybrid-based composite systems (modules). LFHIT checks what could be broken by mechanical
damages, which could occur when handling the hybrid. It gives a fast diagnostic of hybrid operability, which is
useful after the reception of a system and before going into longer tests and procedures. Some LFHIT have
already been distributed around the CMS tracker collaboration (USA, Italy…) and some 20 others are under
construction.
Figure 4 : The portable tester LFHIT mounted with an hybrid circuit.
2.1.4.2. Connection to the CMS tracker database : creation of XML files
X. Rouby (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
The compatibility between FHIT output data and the CMS tracker database is obviously required in
order to encode the data coming from hybrid tests at CERN, Strasbourg or in the industry. As both the FHIT
setup and the database were in development and constant evolution, the solution was choosen to produce test
data in ASCII files and to translate it afterwards into XML database compatible files. The output of an industrial
test comes from two independent sources : the front end electronics (for both the connectivity and the electrical
tests) and the internal digitalization board – ARC – (for the functional test).
70
These two sources are managed by the FHITS user-interface. But the different nature of the data implies
an easier handling with the C language than with the low effective LabVIEW routines. Moreover, the
factorization of the data production and the XML parsing made easier the backward compatibility with older
version of the test system. This was crucial as the database itself was in development and not well defined at
first. This software development was performed in close collaboration with IReS in Strasbourg.
[1] Testing and characterizing CMS tracker front-end hybrids, X. Rouby (2003), Physicalia Magazine, n° 25-3,
pp. 149-158.
[2] http://www.physik.rwth-aachen.de/group/IIIphys/CMS/tracker/en/index.html.
[3] http://www.fynu.ucl.ac.be/themes/he/cms/activities/tracker/hybrids.html.
2.1.5. Temperature distribution tests on the petals of the CMS-Tracker End Caps
L. Bonnet, B. de Callatay, G. Grégoire, O. Militaru (Institut de Physique Nucléaire, Université catholique de
The Institute is responsible of the assembly of detectors supports disposed in wedge structures called
‘petals’. Each petal holds about 26-28 modules, a module having at most two silicon micro-strips sensors and
one read-out electronic circuit (hybrids). The aluminium inserts are small elements integrated within the petal
structures and have two goals, they support the silicon sensors but they also serve as heat collectors. They were
designed by our Institute, together with the cooling pipes integrated in the petal supports, to guarantee the best
heat transfer from the silicon sensors and hybrids components to the cooling liquid, during the operation of the
experiment.
In order to have an accurate view of the temperature distribution for an entire petal during the
experiment, a petal support prototype, with the final design of cooling pipes, was connected to the cooling plant
(one petal has two independent cooling circuits that are connected in series). Cooling liquid parameters, such as
flow rate (adjustable in the range (0- 3.20) l/min via an OMRON regulator) and differential pressure (pressure
difference between the petal inlet and outlet) can be monitored and controlled during the tests.
Two, fairly different, set-ups were used to perform the tests, on the same petal structure. One setup,
common to both tests, consisted on 40 resistors, fixed on circular metal plates, with an equal number of Pt100
temperature probes. The resistors were connected to low voltage power supply. The power developed on each
resistor can reach up to 3 W: in this way the maximum heat load expected on the real petal, around 80 W, can be
simulated. The resistors were fixed along the pipes, on separate inserts, while additional probes placed at other
inserts checked the temperature.
Initially the tests (from July 2003) were performed with an thin aluminium plate mimicking a real
module; resistors were stuck to the plate and connected to a low voltage power supply. Several Pt100 probes
glued on the opposite side determine the temperature gradient on the Al plate. This small unit could give us
valuable informations about the temperature distribution on the module itself.
71
Figure 1 : A front petal undergoing thermal tests. The small brass structures connected by
multiwire cables are programmable heat loads. A mockup of a module is visible at
the upper left hand corner. The heating resistors are the brown rectangles.
For the second test (September 2003) we replaced the aluminium plate with a real dummy silicon
module. With one flat resistor (embedded in kapton foil) in the position where the hybrid should be, three
resistors (same kapton foil geometry) to heat the silicon substrate, the module was mounted on the petal, screwed
to 4 heat collectors. Four Pt100 temperature probes were stick on the silicon plate backside. The set-up can be
seen in the picture.
The data were taken in real CMS conditions, -20°C temperature for the cooling liquid and realistic
heat loads on the modules. Inside the test box, both room temperature and cold air was flushed inside.
The complex set-up was controlled and monitored by Agilent HP34970A, for temperature and relative
humidity, flow rate and differential pressure of the cooling liquid. The data acquisition was done via PC (Win98
platform) with LabView 6.1 interface.
72
Figure 2 : Display of the monitor during thermal tests of petals. The central part sketches a petal; the green boxes
represent the positions of the heat loads; the grey boxes are interleaved temperature probes. Additional
menus at right show the flow conditions. Each row in the four columns allows to set the heat load and/or
to measure the temperature.
2.1.6. CMS tracker Petal and Module tests
C. Delaere, Gh. Grégoire, T. Keutgen, V. Lemaître, O. Militaru, O. van der Aa (Institut de Physique Nucléaire,
Université catholique de Louvain, Louvain-la-Neuve, Belgium)
As a qualification center for the CMS tracker end-caps (TEC) assembly, the Nuclear Physics Institute is
involved into the deployment of software and hardware necessary to achieve the full tests required to qualify the
modules and petals which will be included into the tracker. The module test set-up is fully operational and has
been used to check his functionality’s with the available modules in Louvain-la-Neuve (only three for the
moment). For the Petal integration set-up, the final configuration is still in discussion in the CMS collaboration.
The hardware and software are in development and should be completed in a few months.
I. Module Test
The hardware system, shown in Figure 1, is set-up and tested to match the conditions required by the
CMS collaboration.
73
Figure 1.
A cold box, containing up to 6 modules, is flushed by dry air to insure a very low humidity
environment. A cooling plant allows to set the temperature in the cold box at a value between –20° and 20°
Celsius.
The acquisition system is divided in two parts [1] : the slow control and the APV readout system (DAQ).
The slow control system handles the high voltage necessary to bias the detectors, monitors the temperature and
humidity conditions and measures the detector leakage current. It is controlled via LabView on Windows
platform. The fast DAQ system is running in a Linux machine. A software [2] has been developed in Lyon and
Antwerpen for the APV’s readout. It allows the users to perform several tests with different ambient conditions
in order to check the quality of the silicon strip modules placed in the cold box. An example of scenario is shown
in Figure 2.
Figure 2.
74
In this scenario, the DAQ control system the temperature of the Cooling Plant (Temperature Set) and
the HV via a TCP/IP connection to the slow control. As a function of time, the slow control measures the frame
and ambient temperatures, the relative humidity in the cold box, the HV and leakage current. All these values are
sent to the DAQ system for recording. For each temperature values, pedestal measurements, noise, IV curve and
others tests are performed on the detectors. Figure 3 shows samples of tests performed at different temperatures.
These results are in agreement with the module assembly center [3].
Figure 3.
All the results obtained for each module are recorded into a root and XML files. The XML file has a
specific format in order to be sent to the database of the CMS collaboration [4].
II. Petal Burn-in
The set-up shown in Figure 4 is still in development for the Petal integration centers.
Figure 4.
75
An active fridge was modified to handle a petal. The temperatures of the fridge and cooling plant are
controlled by the slow control PC. Several temperature and humidity probes, positioned in different points of the
fridge, give the real status inside the fridge to the slow control. In each petal, up to 28 modules should be bias.
For this purpose, a HV Switching Box allows to bias up to 24 lines individually and read the resulting leakage
current. The FED module, inserted in the DAQ PC, via Opto-Electrical Converter (OEC) and multiplexers
(MUX), does the readout of the APV's. Finally, a Interlock board, connected to the Slow Control, checks the
hardware conditions and can switch off HV, LV, Cooling Plant and fridge devices in order to protect the petal
from external damages as much as possible.
For the software point of view, new LtStruct [5] software is being developed for the control of this set-up
by the DAQ system.
This set-up should be operational for the beginning of 2004.
[1] Rapport CYCLONE 2002
[2] http://cmsdoc.cern.ch/cms/cmt/System_aspects/Daq/ and
http://hep.uia.ac.be/cms/testing/software/ltswdoc.html
[3] http://www.physik.rwth-aachen.de/group/IIIphys/CMS/tracker/en/archome.html
[4] http://c.home.cern.ch/c/cmstrkdb/public/html/
[5] http://hep.uia.ac.be/cms/testing/software/ltstruct/ltstruc.html
2.2. Activités liées à la sélection et à la reconstruction des événements
C. Delaere, S. de Visscher, Th. Keutgen, G. Leibenguth, V. Lemaître, A. Ninane, V. Roberfroid, O. van der Aa
(Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
The CMS trigger has been designed in two steps. The first rejection (Level 1) is coded in a FPGA
cluster and uses only rough information coming from restricted regions of the detector. It is by design fast and
the second step (usually called the High Level Trigger, HLT) refines this information by using more
sophisticated algorithms. To contribute more actively to this task, the High Energy Group has adopted the
following two strategies: the full study of one physics channel has begun and the design of a new prototype to
merge all these “sophisticated algorithms” has been proposed to the CMS collaboration. To ease the realisation
of these projects, the deployment of the CMS computer cluster in Louvain has been pursued.
2.2.1. HLT Steering Code Prototype
Résumé : Un logiciel permettant l’intégration des algorithmes de reconstruction développés dans le contexte de
l’expérience CMS est présenté. Ce logiciel est une implementation candidate pour la selection en
ligne des événements au sein de l’infrastructure d’acquisition de CMS.
In the DAQ TDR [1], high level trigger strategies have been evaluated for different types of objects,
namely electrons/photons, muons, taus and jets. In order to prepare the Physics TDR, there is a need for a simple
and common steering code to all algorithms involved in the event selection, since several high level strategies
will be used as a preliminary step in the forecoming activities. In order to integrate all these codes it is also
necessary to provide a simple interface where the implementation of the selection algorithms can be put.
The necessity to have a global interface between these different topologies has lead to the creation of a
HLT prototype. It is now a part of the official CMS ORCA [2] software, and provides the following
functionalities :
•
•
•
•
Dynamic HLT definition,
Possible optimization of the HLT sequence,
Boolean HLT decision (yes or no),
Full HLT response (bit pattern).
It is common practice to consider the trigger as a logical “or” of several trigger elements. More
generally, a trigger (e.g. the HLT) is a logical equation, and can therefore be represented as a binary tree. This
allows for more flexibility, and features like automatic prescale or combined sub triggers, commonly found in L3
triggers of past experiments.
76
Figure 1 : UML diagram of the HLT steering code prototype. Dashed lines are used for
pointer relations while full lines represents a relation of inheritance.
The UML diagram of Figure 1 shows how the various classes are related. The HighLevelTriggerLevel
contains the basic elements for the representation of the HLT decision logic in a binary tree. The HLT response
is recursively evaluated, and the tree leaves correspond to the lowest HLT trigger level. More precisely, the
evaluation request is propagated recursively from the root element up to all leaves. The actual evaluation then
starts from the leaves down to the root, going through all the HLT steps and stopping as soon as one element in
the chain fails. This results in an evaluation sequence that can be optimized at each node.
The design of the HLT prototype enables to dynamically build the tree of elements at runtime. An
example of the use of that feature is the HighLevelTriggerXML class. When the HLT is built (during the first
event evaluation), the XML file is read and translated into a binary tree. This allows for a fast analysis cycle
since no compilation is needed.
There are lots of advantages using XML. The DTD can be used to restrict the allowed connections
between trigger elements. There are simple tools available to check the validity of xml files; it is relatively easy
to write a helper application (e.g. a GUI) producing the XML file.
This prototype is currently under study, and is a candidate to be used for the actual on-line selection of
the data acquisition system.
[1] CERN/LHCC 2002-26 CMS Collaboration, ”The Trigger and Data Acquisition project, Volume II.Data
Acquisition & High-Level Trigger. Technical Design Report”.
[2] CMS-CR 1999-018 C. Charlot, ”On Demand Reconstruction within ORCA”
2.2.2. Standard model Higgs boson study: WW decays
Résumé : Analyse de l’observabilité d’un Higgs du Modèle Standard produit avec un W et se désintégrant en
deux W.
A major objective of the CMS physics TDR, planned for December 2004, is to demonstrate the
readiness of the people and of the software for fully featured physics analysis.
In that context, we started to investigate the study of the decay channel H→WW where the Higgs
boson, at intermediate mass (110-200 GeV), is produced in association with a W boson. This process is thus
characterized by 3 W's in the intermediate state (Figure 1).
77
Figure 1 : Feynmann diagram of the channel HW→WWW.
Amongst the numerous final states, two clear signatures are the same-sign leptons channel and the three
leptons one. Previous generator-level ATLAS studies [1,2,3] show that those two event classes can give a
significant contribution to the discovery potential. Those channels are also needed for a global study of Higgs
couplings to fermions (especially to the top quark) and bosons.
If there is a fermiophobic Higgs boson, this channel can even be one of the only sensible one, since the
Higgs-W coupling is involved both in the production and in the decay.
From a theoretical point of view, this process has been computed at NLO. The corrections to the LO
calculation are of the order of 10 % at the LHC so that it can be considered under control.
Figure 2 : Cross section for the channel HW→WWW as a function of the Higgs mass.
This activity is just starting and will benefit from the new software environment installed in Louvain-laNeuve.
A preliminary study of the backgrounds to be considered as well as of the tools to be used to generate
them has been carried on. The results for the 3 leptons channel are shown in table 1. The signal cross-section is
presented on the Figure 2.
Higgs Mass
(GeV/c2)
115
140
170
Cross section
σ.BR (3 l)
σ.BR (2 ss l)
2.08 pb
1.12 pb
0.585 pb
3.4 fb
9.7 fb
9.0 fb
22 fb
63 fb
59 fb
Table 1 : Cross section for WH production and cross section time the branching ratio for the two channels
WH→WWW → l± ν l± ν l± ν (3 l) and WH→WWW → l± ν l± ν jet-jet (2 ss l) for three Higgs
masses.
[1] V. Cavasinni, D. Costanzo, « Search for WH → WWW → l± ν l± ν jet-jet using like-sign leptons», ATLASPHYS-2000-013.
[2] W. Bonivento, « First look at a SM Higgs boson search with a tri-lepton signal », ATLAS-PHYS-2000011.
[3] K. Jakobs, « A study of the associated production WH, H → WW → lnulnu », ATLAS-Phys-2000-008.
78
2.2.3. Multi-object trigger scheme, an example
Résumé : Analyse de l’observabilite d’un higgs supersymmetrique lourd ayant pour etat finaux des leptons
taus. L’analyse est poursuive dans un regime a grande valeur de tanβ.
The Minimal SuperSymmetric Model (MSSM) is currently one of the most popular extensions to the Standard
Model, describing particle interactions at energies in the TeV range. The model predicts two Higgs doublet fields
yielding five physical Higgs bosons, which might be all in the reach of the LHC. For some parameter choices (in
particular: large tan β), the H and A boson couplings to the down type fermions (mainly bb and ττ) can be
greatly enhanced with large production cross sections in association with b quarks. For H → ττ, the final states
ll, l+jets, jets+jets (where jets mean here the observed hadronic tau decay and l stands for electron or muon) have
been investigated in CMS [1]. The e + jets channel has been chosen for a full analysis, and it represents about
20% of the total branching ratio. To optimize the channel potential, one would combine the electron and the jet
triggers to maximize the trigger efficiency for a given rate (fixed by the limited technology of the data
acquisition system). It has been shown [1] that the selection efficiency of the signal is improved by 10 % when
one uses a e-jet combined trigger instead of a single electron trigger, for a reasonable rate increase. However, a
detailed analysis of this channel, including as much background as possible, is mandatory to obtain the
sensitivity gained by the combined trigger. Using the new CMS computer cluster, the signal as well as most of
the background is currently being generated. All the background listed in Table 1 has been considered for the
analysis. A preliminary analysis as been pursued on the generated pythia events. The expected number of
events observed for an integrated luminosity of 864 pb-1 is shown on figure 1.
Figure 1 : Expected number of signal and background events after selection. The Z peak is
not included.
Table 1 : Number of events generated and igitised in Louvain together with their cross sections. *To deal with
acceptable cross section, a cut on the mass invariant has been applied.
Process
Z/γ
tt(lvlv)
tt(lvqq)
Wtb(lvlv)
Wtb(lvqq)
W+jet
Signal
# of gen evt
48 000
0
0
0
37 000
0
49 000
σ (in pb)
1192*
23.2
69.5
31.2
64.4
683.3*
1.8
Table 1.
[1] CERN/LHCC 2002-26 CMS Collaboration, ”The Trigger and Data Acquisition project, Volume II.Data
Acquisition & High-Level Trigger. Technical Design Report”.
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2.2.4. Development of a computing cluster
Résumé : La simulation du détecteur CMS a nécessité l’installation d’une grappe de calcul. 12 machines
biprocesseurs PIII ont été installées et sont actuellement utilisées pour les différentes analyses
présentées dans ce rapport.
To permit the test of the new HLT software as well as the Monte Carlo simulation production, the
development of a local computing cluster is carried on.
Deployment of the cluster means both software and hardware activities. From the hardware point of
view, we have chosen to develop the system in several steps. The two first steps were achieved in 2002 with the
installation of a RAID (Redundant Array of Independent Disks) storage device as well as a manager and
software repository (Dell Precision™ workstation 530) and with the proof-of-concept using 8 existing Celeron
machines.
During the year 2003, the third step has been to buy, setup and bring to work 12 1U Dell PowerEdge™
1650 servers with two Intel® Pentium® III processors at 1.4 GHz and 512 MB. The interconnection of those
components is shown on Figure 1.
A stress procedure has been imagined and executed in order to test the mass storage arrays from the
cluster nodes. Simultaneous transfers 1GB files have been started from the computing nodes to the RAID arrays.
A rate up to 75MB/s has been reached and maintained during the whole transfer when using a combination of
rcp for data transfer and RAID0 for storage. It must be noticed that switching either to NFS or RAID5 lead to
problems respectively with the NFS daemon cache and the RAID firmware.
The Red Hat® Linux® 7.3 operating system, currently used at CERN by the CMS collaboration, has
been installed on every machine as well as all the CMS-specific software.
Figure 1: General architecture of the installed cluster [1].
The CMS software involves several modules to pursue event generation, simulation, reconstruction and
persistent storage. Two major version of the reconstruction software ORCA (ORCA 7.2.2 and ORCA 7.5.1)
have been successfully used. This allows the simulation, reconstruction and analysis of various signatures, or the
production of Monte Carlo events according to the new GRID-compatible standard adopted by the collaboration.
[1] Christophe Delaere; Thomas Keutgen, Ph.D.; Guillaume Leibenguth, Ph.D.; Vincent Lemaitre, Ph.D.;
Alain Ninane, Ph.D.; and Olivier van der Aa; Solving High-Energy Physics Using a Dell HPC Cluster at
the Université catholique de Louvain. Dell Power Solutions August 2003.
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2.3. Activités liées à l’étude des interactions de photons de haute énergie au
LHC
J. de Favereau (FRIA), O. Militaru, K. Piotrzkowski, X. Rouby (Institut de Physique Nucléaire, Université
Two-photon physics has been widely studied at ee colliders since there are large fluxes of virtual
photons associated with the electron beams. The proton beam energy of the LHC will be so high that the
effective luminosity of γγ collisions will permit new studies of high-energy γγ interactions. These measurements
are complementary to the ‘‘base-line’’ pp studies and can be carried out simultaneously. The main experimental
issue is the selection of such interactions among billions of usual proton-proton collisions. This is most of the
time impossible with the main CMS detector only. The protons which emitted photons usually continue in the
beam pipe − emission of a low virtuality (Q²) photon results in a small scattering angle of ~100 µrad. In case of a
high Q² photon the protons might also not survive the interaction. However, for low Q² quasi-real photons, the
scattered protons can be measured using dedicated detectors, the so-called roman pots (RP), far away from the
CMS interaction point (IP), thus effectively enabling the photoproduction tagging [1]. Moreover, in the similar
way a study of photon-proton interactions which occur at even higher energies will be possible.
This activity is to a large extend pursued within the framework of the CMS-TOTEM group studying
possibility of extending the CMS research program by the physics studies using the forward detectors. In
December 2003 the CMS management board very favorably evaluated the results of this activity and asked for
preparation of an Expression of Interest to the LHC Committee, expressing the intention of extending
accordingly the CMS scientific scope. The EoI was submitted in March 2004, and will be followed by a Letter of
Intent in early 2005.
There are related technical issues, which must be solved, as for example the way of integrating of such
detectors into the CMS trigger and data acquisition systems, or choosing the right detector technology to be used
in the RPs. The latter is studied at FYNU within the collaboration RD39.
Figure 1 : Ratio of the effective γγ (left and center plot) and γp luminosity (right plot), to the nominal luminosity of pp
collisions, as a function of minimum center-of-mass energy Wcut (of the γγ and γp collisions, respectively)
assumed in calculations. The curves have been obtained with PHOTIA. The left plot corresponds to the
elastic case when both colliding protons survive the interaction, and the center plot shows the luminosity
curve for the inelastic case when only one proton survives. The right plot corresponds to the elastic γp case.
2.3.1. Monte Carlo event generation and simulation in CMS detector
J. de Favereau (FRIA) et K. Piotrzkowski (Institut de Physique Nucléaire, Université catholique de Louvain,
Louvain-la-Neuve, Belgium)
To evaluate properly the physics potential of photon interactions in CMS new analysis tools had to be
prepared. Primarily, there was no proper event generator of photon interactions in pp collisions available,
therefore the existing general-purpose event generator PYTHIA has been modified as to allow for an effective
simulation of high energy γγ and γp collisions. In Figure 1, the luminosity curves for such collisions at the LHC
obtained with PHOTIA (a tentative name of the modified PYTHIA generator) are shown. One can see that a
significant luminosity, close to 1% of the pp luminosity, can be obtained for the γγ collisions at W > 100 GeV, or
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for the γp collisions at the corresponding W > 1 TeV! The new generator has been successfully integrated into
the CMS software platform using the CMKIN program. Then, the full simulation of the CMS detector response
became possible (using OSCAR) as well as the full CMS trigger simulation and event reconstruction (using
ORCA). In Figure 2, a CMS event display is shown corresponding to the production of W boson in photonproton interactions.
Figure 2 : The event display showing a γp → W jet event (with the W boson decaying into eν) in the CMS detector.
This development is crucial for further more detailed studies. In particular, the CMS trigger efficiency
and its possible optimization can be studied. Figure 3 demonstrates a first step in this direction, showing a
distribution of the reconstructed electron transverse momentum for the γγ → WW events in CMS, when at least
one W boson decays into eν, and assuming a nominal first level trigger configuration.
Figure 3 : Distribution of the transverse momentum in GeVof the decay electrons of the W
bosons produced in γγ fusion at the LHC. The statistics corresponds to a few years
of running LHC at low luminosity.
These first results show already that high efficiency of triggering such events can be expected at CMS
even without introducing dedicated trigger algorithms for the photoproduction case. Similar study has been done
for the top pair production in γp interactions at the LHC. In Figure 4 the similar plot is shown for the electrons
coming from the top quark decays, where the top pairs are predominantly produced in the process of the photongluon fusion.
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Figure 4 : Distribution of the transverse momentum in GeV of the electrons from the decays
of top quarks produced in γg fusionat the LHC. The statistics corresponds to a
year of running LHC at low luminosity. The line indicates the nominal trigger
threshold for electrons in CMS.
The high trigger efficiency is expected for these events too, and the large statistics of such data opens
very interesting possibilities of precision measurements of top quark properties in the photon interactions. All
these initial studies will be continued using more detailed simulation of the photon events (including the
measurement of very forward protons) and more complex and complete event reconstruction and analysis tools.
2.3.2. Studies of the triple gauge coupling γWW in photoproduction at the LHC
Jérôme de Favereau (FRIA) (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-laNeuve, Belgium)
As a first step in evaluating the physics potential of studying photon interactions at the LHC, the
anomalous photoproduction of W bosons has been considered in γγ and γp interactions. For that, the crosssections has been calculated (at a tree level) basing on an effective lagrangian and using the program CalcHEP.
Figure 5 : Feynman diagrams for two-photon production of W pairs and a single W boson
production via γ-quark interactions in γp collisions; both involving triple gauge
couplings γWW.
Two dimensionless parameters are introduced, λ and κ, related to the electric quadrupole and magnetic
dipole moments of the W boson (in the SM κ=1 and λ=0). Then, the PHOTIA events have been accordingly reweighted to describe the change of the SM cross-sections. The two-photon W pair production is particularly
sensitive to these effects, as the dominant diagram involves two γWW couplings, see Figure 5. The first
preliminary results indeed show a large sensitivity at the LHC to the anomalous values of these parameters, as
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shown below. For example, in case of the γγ → WW process, λ = −0.03 results in almost 20 % increase of the
cross-section.
Figure 6 : The ratios of the total cross-section for the processes, γp → WX (left plot) and γγ → WW (right plot), to
their values in the Standard Model, as a function of the λ parameter.
λ=0.10
0.03
0.01
0.0
W
Figure 7 : The event distributions for γγ → WW (upper plot) and γp → WX (lower plot) as a
function of the center-of-mass energy (in GeV) in γγ and γp collisions,
respectively. The data statistics corresponds to about one year for the γγ case, and
one month for the γp one, of the LHC running at low luminosity. Four curves
correspond to four values of the anomalous parameter λ of 0.1, 0.03, 0.01 and 0.0.
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It is interesting to note in this context the recent limits, - 0.039 < λ < 0.005, from all the LEP II data
(Moriond, 2004).
In addition, the energy dependence of the cross-sections has been studied. In Figure 7, event distribution
is shown as a function of center-of-mass-energy, for the production of W pairs in γγ interactions as well as for the
production of a single W boson in γp collisions.
The results show a strong W dependence and clearly demonstrate a large potential of such studies at the
LHC. Further studies will be done including a full simulation of event reconstruction and treatment of the
background events.
2.3.3. Simulation of the proton transport in the LHC beam-line
The efficiency of photoproduction tagging at the LHC depends, both on the performance of the Roman
Pot detectors and on the geometrical acceptance of the LHC beam-line for the forward-scattered protons. To
study in detail the latter a work on the fast Monte Carlo simulation has been initiated. This tool will also serve to
optimize the layout and performance of the proton detectors. First analyses of the LHC beam-line optics and has
been reported to the CMS-TOTEM group. This development will be continued having in mind an eventual
integration of such a Monte Carlo program in the CMS simulation framework.
2.3.4. Two-photon production of the lepton pairs at the LHC
K. Piotrzkowski (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
in collaboration with D. Bocian (CERN/Kraków)
The possibility of using two-photon forward lepton pair production has been proposed for a precise
luminosity measurements at the LHC [2]. The cross-section for very forward two-photon production of ee pairs in
proton-proton collisions can be calculated within QED to an accuracy better than 1 %, and at LHC energies the
production of high-energy pairs becomes sizeable. The main characteristics of the reaction pp → ppee are the
very small (of the order of the electron mass) invariant mass and transverse momentum, pT, of the produced pairs
(see Figure 8). Inelastic two-photon production of ee pairs, where one or both protons break up, has a
significantly wider distribution of pair pT. For hadronic reactions, the typical energy scale is the pion mass or
higher. This corresponds to very small emission angles of produced electrons and positrons with respect to the
colliding protons – for example, for energies of a few GeV these angles are of the order of 1 mrad. Detection of
these events requires therefore detectors, which are installed very close to the proton beam.
The luminosity measurement for ion collisions at the LHC is so far an unsolved problem. Usual method
of pp luminosity normalization using the optical theorem and measurement of elastic and inelastic hadronic
interactions is not applicable here due to experimental difficulties, in particular necessity of measurement of
elastic ion scattering at extremely small angles. On the other hand, two-photon pair production is particularly
interesting in this context – two-photon interactions in ion collisions are enhanced owing to the coherence
effects. For forward pair production the enhancement scales as Z4, whereas the hadronic backgrounds scale
approximately as A2, where A and Z are atomic numbers of the colliding ions (here we assumed collisions of
same ion species). In addition, the inelastic two-photon production is supressed in coherent ion interactions. The
full coherence is ensured for the very forward two-photon process AA → AAee thanks to very small virtualities
of the exchanged photons – in other words, this process usually occurs at distances where ions can be regarded
as pointlike particles with charges Z.
85
Figure 8 : Feynman diagram of the two-photon process with definition of kinematical
variables; in particular acoplanarity angle φ is introduced, as an azimuthal angle
between the transverse momenta of the produced electron and positron.
Recently, a new detector CASTOR in forward direction has been proposed for studies of the ion
collisions in the CMS experiment. Below, the following performance of this detector is assumed in simulations of
the forward pair measurements: The CASTOR (geometrical) angular acceptance extends between 2.2 and 8.2
mrad, and the relative energy resolution is 20 %/√E, where energy E is given in GeV; the position resolution is
0.5 mm. In the detector simulation the gaussian resolutions are used with the quoted widths for smearing the
‘true’ variables. In addition, the smearing due to the ion beam divergence and spatial distribution at the
interaction point is taken into account. All quoted results correspond to an energy range for electrons and
positrons of 3–20 GeV. The lower end is a compromise between need for a maximal cross-section and the good
performance of CASTOR. Upper end is rather arbitrary and changes little the results even if increased
significantly.
LPAIR event generator is used for simulation of this process. This is a leading order, Born-level,
generator initially constructed for proton interactions. Because of the Born approximation its results cannot be
trusted if the product of two ion charges exceeds largely 137, i.e. if αZ1Z2 >> 1. Therefore, we only present
results obtained for proton-ion collisions and light ion collisions. Heavy ion case requires semi-classical methods
of calculation, and is not discussed here. The LPAIR generator has been modified to allow for ion collisions by
scaling the charges of the colliding particles by Z and increasing the radius of spatial charge distribution by A1/3
with respect to the nominal proton case. The same shape, though, of the electromagnetic form factor, according
to the so-called dipole approximation, has been assumed. The simulations were done at corresponding beam
energies of 7, 140 and 574 TeV for proton, calcium and lead beams, respectively.
Figure 9 : Distributions of the acoplanarity angle, transverse momentum and invariant mass of the forward pairs
produced within the CASTOR acceptance in calcium-calcium collisions. The reconstructed
distributions are overlaid.
In Figure 9 the distributions of the acoplanarity angle and transverse momentum of pairs detected in
CASTOR are shown. The acoplanarity distribution shows the unique for the two-photon production sharp peak
around zero. Around 80 % events are contained in the range ± 50°, moreover the pT distribution is very narrow
86
with majority of events with pT < 20 MeV/c ! This demonstrates clearly the capability of the CASTOR detector
of identifying and reconstructing the two-photon events. As a result the luminosity measurement using this
technique has became part of the CASTOR proposal.
Results of this work will be the subject of two publications in preparation. In parallel, an activity is
pursued on the experimental aspects of the precise luminosity measurement in pp collisions.
[1] K.Piotrzkowski, Phys. Rev. D63 (2001) 071502(R); hep-ex/0201027.
[2] K. Piotrzkowski, Proposal for Luminosity Measurement at LHC, ATLAS Note ATL-PHYS 96-077 (1996).
2.4. Phénoménologie au LHC
Les chercheurs de l’UCL sont activement impliqués dans la préparation des futures analyses physiques
qui pourraient être réalisées au LHC. Les sujets abordés par le groupe de Louvain se situent dans le cadre de
l’étude du secteur scalaire de la supersymétrie, du Modèle Standard ou autres modèles exotiques tels que ceux
basés sur l’hypothèse de l’existence de dimensions spatiales macroscopiques supplémentaires. Plus précisément,
les études portent sur :
Les possibilités d'observation d'un Higgs léger dans des canaux de désintégration et production
différents de ceux habituellement proposés (gluon + gluon → H → γ + γ, et production associée de t-tbar suivie
de la désintégration du Higgs en b-bbar ).
L’intérêt d'observation d’éventuelles représentations exotiques du secteur de Higgs.
La possibilité d’observer des tours excitées de Kalusza-Klein prédites par les théories possédant des
dimensions spatiales macroscopiques supplémentaires.
La possibilité d’étudier les collisions entre photons (provenant de la radiation des protons incidents) en
vue d’observer des processus comme la production de Higgs, de charginos, de paires de W et peut-être aussi de
quarks top.
2.4.1. Techniques numériques pour le calcul de diagrammes de Feynman à une boucle
E. Burton, J. Govaerts (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve,
Belgium)
Abstract : The Standard Model background for the production of a Z0 pair at the LHC involves gluon fusion
through quark box diagrams. The computation of loop-integrals requires the use of a numerical
technique recently developed by Passarino et al. This technique is being encoded into a general and
user friendly library reliable for all values of external momenta and internal masses.
L’étude phénoménologique de modèles au-delà du Modèle Standard (Large Extra Dimensions, Little
Higgs models, …) dans les collisions proton-proton au LHC nécessite la connaissance précise du bruit de fond
du Modèle Standard. Dans le cas de la production d’une paire de bosons de jauge Z0, dont la désintégration
quadri-fermionique laisse une trace très claire dans les détecteurs, le bruit de fond comporte, entre autres, le
diagramme avec une boîte de quarks provenant de la fusion de deux gluons. Bien que ce diagramme soit au nextto-next-to leading order, la correction qu’il apporte au bruit de fond total est non-négligeable étant donnés,
d’une part, le running décroissant de la constante de couplage αs et, d’autre part, la grande luminosité des gluons.
Le calcul des amplitudes d’hélicité du processus gg → ZZ a été fait par Glover et van der Bij[1] d’après
les techniques standard de réduction d’intégrales tensorielles en combinaisons linéaires d’intégrales scalaires
proposées par Passarino et Veltman, et d’évaluations analytiques des intégrales scalaires en terme de fonctions
logarithmes et dilogarithmes proposées par ‘t Hooft et Veltman. Pour éviter les instabilités numériques, les
expressions obtenues sont développées en série de Taylor autour de mq = 0 pour les quarks légers et différentes
coupures cinématiques arbitraires sont effectuées dans les régions où les instabilités ne peuvent être évitées.
Afin de ne pas reproduire simplement les résultats précédents, nous avons recalculé les amplitudes
d’hélicité pour gg → ZZ à l’aide de LoopTools. LoopTools est un programme qui interface en Fortran, en C++ et
en Mathematica, le package FF (version 1.6). Ce dernier encode les formules des coefficients de Passarino87
Veltman et les expressions analytiques des intégrales scalaires. L’emploi d’un tel outil ne permet cependant pas
d’éviter l’apparition d’instabilités numériques ; celles-ci ont plusieurs causes. Tout d’abord l’évaluation de
fonctions spéciales dans des domaines proches de leurs singularités. Ensuite, l’apparition au dénominateur de
déterminants de Gram qui peuvent s’annuler en certains points de l’espace de phase. Enfin, le calcul de
déterminants de matrices dont les éléments ont des échelles de valeurs très différentes, induit des multiplications
de nombres éloignés. Mentionnons également la soustraction de nombres relativement proches. Tout ceci
conduit à des pertes significatives de précision. En résumé, l’emploi de LoopTools n’a pas permis d’obtenir des
résultats satisfaisants. Il existe une version plus récente de FF (version 2.0) où la stabilité numérique est
améliorée, principalement dans le calcul des déterminants. Il s’agira de déterminer dans quelle mesure les
résultats fournis par FF2.0 seront plus fiables.
Afin de limiter les problèmes numériques, on a tenté d’utiliser une méthode alternative de réduction
tenseur-scalaire proposée par R. Pittau[2] : cette technique consiste à transformer des intégrales de rang supérieur
à 1 en une somme d’intégrales de rang 1 et d’intégrales scalaires par décomposition des quadri-impulsions et en
utilisant l’algèbre spinorielle pour des particules de masse nulle. En définitive, cette méthode a été abandonnée
car elle augmentait considérablement le nombre de termes à évaluer sans évacuer complètement le problème des
déterminants cinématiques qui apparaissent toujours au dénominateur lors de la réduction des intégrales de rang
1.
Finalement, c’est sous un nouvel angle que le problème de l’évaluation des intégrales de boucles a été
abordé. En septembre 2002, G. Passarino et ses collaborateurs ont proposé un algorithme numérique général
pour l’évaluation des diagrammes de Feynman à une boucle[3]. Après avoir effectué l’intégrale sur la quadriimpulsion de la boucle par régularisation dimensionnelle, l’intégrale restante sur les paramètres de Feynman est
transformée, à l’aide du théorème de Bernstein-Tkachov et d’intégrations par partie, en somme d’intégrales
multidimensionnelles de fonctions logarithmiques. Les singularités du diagramme sont regroupées dans les zéros
d’un facteur qui apparaît au dénominateur. Autour des points singuliers, cette méthode fait également appel à des
techniques spécifiques telles que la décomposition sectorielle et les transformées de Mellin-Barnes.
Globalement, cette méthode assure un meilleur contrôle de la stabilité en tous les points de l’espace de phase et
permet l’introduction de masses complexes. Elle permet également de tenir compte des divergences infrarouges.
L’encodage général de cet algorithme est en cours, en collaboration avec l’auteur. Cela nécessite entre
autre une évaluation précise des fonctions spéciales de base et des routines d’intégration fiables. À ce titre, nous
utilisons CUBPACK, implémentée en Fortran95 par R. Cools (KUL), une routine d’intégration
multidimensionnelle par méthode globale adaptative.
Les techniques numériques de résolution d’intégrales de boucles, parce que plus générales, plus fiables
et plus rapides que les techniques analytiques standard, trouvent surtout leur raison d’être dans l’évaluation des
diagrammes à deux boucles qui s’insère dans le vaste projet Topside. Ce projet a pour but de créer un générateur
complet à deux boucles des observables de Modèle Standard. Le calcul des corrections radiatives est
indispensable pour réduire l’incertitude théorique dont la valeur pourrait être comparable à d’éventuelles
signatures d’une nouvelle physique au-delà du Modèle Standard.
[1] E.W.N. Glover, J.J. van der Bij, Nucl. Phys. B321 (1989) 561-590.
[2] R. Pittau, Comput. Phys. Comm. 104 (1997) 23-36 ; ibid 111 (1998) 48-56.
[3] G. Passarino et al., Nucl. Phys. B650 (2003) 162-228.
2.5. Physique théorique
2.5.1. Problèmes de quantification et compactifications de théorie des cordes
J. Govaerts, F. Payen (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve)
Abstract : We first discuss problems related to the quantisation of particles and strings in various situations.
Then we study the production at tree-level of highly excited closed bosonic string states associated to
quantum gravity black holes, and its sensitivity to the compactification mechanism of the extra spatial
dimensions.
La physique fondamentale moderne nous offre une description incroyablement précise du monde des
particules élémentaires et de leurs interactions. Mais malgré ses grands succès, elle repose sur deux édifices
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conceptuels, la relativité générale et le modèle standard, qui sont fondamentalement incompatibles, car la
description de la gravitation proposée par Einstein résiste à toute tentative de quantification. A l'heure actuelle,
seules les théories des supercordes proposent un cadre assez large pour unifier de manière cohérente les
interactions fondamentales. Elles semblent former différentes facettes d'une théorie unique, la théorie M, qui
pourrait constituer la description ultime de l'univers.
D’une part, la compréhension profonde de la théorie des cordes est un des grands défis des physiciens
de ce siècle. Dans ce contexte, plusieurs problèmes de quantification ont été abordés cette année :
-
Nous avons poursuivi l’étude de particules et cordes bosoniques libres dans un espace-temps dont un certain
nombre de dimensions spatiales sont compactifiées sur un tore. L'idée consiste à prendre en considération les
degrés de liberté topologiques[1] caractérisant la représentation de l'algèbre de Heisenberg qui apparaît lors de
la quantification de la position et l'impulsion d’une particule ou du centre de masse d’une corde. L'analyse
montre l'équivalence de cette approche au couplage du système à des champs extérieurs constants, permettant
de jeter un regard nouveau sur une telle interaction. Diverses images duales, encore incomplètes, ont été
développées, entre les théories de cordes ouvertes et fermées, et l’image T-duale faisant intervenir des
configurations de D-branes pour le secteur des cordes ouvertes.
-
Nous avons entamé l’étude de cordes bosoniques et supercordes ouvertes en présence d'une onde plane
électromagnétique, exemple simple d’interaction avec un champ externe dépendant du temps.
-
Nous avons commencé à étudier la dynamique de particules et cordes bosoniques représentées non plus par
de simples coordonnées, mais par des matrices hermitiennes accompagnées d'une symétrie de jauge non
abélienne sur la surface d’univers, modélisant ainsi une possible géométrie non commutative de l’espacetemps. En effet, dans certaines situations et limites spécifiques, la théorie des cordes révèle l’existence de tels
degrés de liberté dans un régime quantique pour l’interaction gravitationnelle.
D’autre part, dans le cadre de modèles phénoménologiques de la gravitation quantique inspirés par la théorie
des cordes, certains groupes[2] ont suggéré la production possible de mini trous noirs à des énergies
accessibles au futur LHC. D’autres[3] ont ensuite prédit la formation d’états excités de cordes précurseurs de
ces trous noirs à des énergies encore inférieures. L’un de nos objectifs cette année consistait à étudier la
production de tels états quantiques.
Considérant l’interaction au tree-level de cordes bosoniques fermées dans un espace-temps compactifié
sur un tore, nous avons formulé les amplitudes de production d’états excités à partir d'états fondamentaux. Des
règles de sélection interdisent un accès direct au secteur des états excités par la compactification des dimensions
spatiales supplémentaires, et le processus paraît à cet ordre insensible à cette compactification, étant entendu que
les expériences et les états physiques observés ne peuvent être réalisés que dans les dimensions non
compactifiées.
[1] J. Govaerts, V.M. Villanueva, Int. J. Mod. Phys. A15 (2000) 4903-4931.
[2] S.B. Giddings, S. Thomas, Phys. Rev. D65 (2002) 056010, arXiv:hep-ph/0106219.
[3] S. Dimopoulos, R. Emparan, Phys. Lett. B526 (2002) 393-398, arXiv:hep-ph/0108060.
2.5.2. Topologie et quantification en théories de jauge à basses dimensions
B. Bertrand, J. Govaerts, J. Martinez-Martinez, F. Payen (Institut de Physique Nucléaire, Université catholique
de Louvain, Louvain-la-Neuve)
Abstract : Through a proper rescaling of the gauge fields, pure Yang-Mills dynamics acquires a form that
reduces to topological quantum field theories of specific types when the gauge coupling constant is
taken either to vanish or become infinite. A research programme studying the potential for an
understanding of the nonperturbative dynamics of Yang-Mills theories, based on this remarkable
feature, has been initiated, starting with the lower dimensional systems.
Depuis la découverte des théories quantiques topologiques de champs[1], la possibilité que la dynamique
non perturbative de théories de Yang-Mills ou de la gravitation puisse être en première approximation gouvernée
par un secteur purement topologique a été suggérée. Par exemple, il est possible de donner une formulation
purement topologique de la gravitation en 2+1 dimensions d’espace-temps, ouvrant la porte à une formulation
non perturbative de la gravitation quantique dans ce cas[2].
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Or, au travers d’une redéfinition, par un facteur d’échelle approprié fonction du couplage de jauge, de la
normalisation des champs de jauge dans une théorie de Yang-Mills, il s’avère en effet possible de considérer
deux limites duales, en terme d’un couplage de jauge tendant soit vers une valeur nulle, soit vers une valeur
infinie, telles que toute théorie de Yang-Mills pure, pour toute dimension et géométrie d’espace-temps, se
réduise à des théories de champs topologiques spécifiques. Il est donc possible de mettre en œuvre un
programme d’étude du potentiel qu’offre un tel point de vue, en élaborant une approche d’emblée basée sur un
secteur essentiellement non perturbatif bien que purement topologique, manifestement invariant de jauge et ne
décrivant donc que des états quantiques physiques, à partir duquel définir une procédure de corrections
systématiques en fonction du couplage de jauge. Notons que dans chacune de ces deux limites, et pour le cas
spécifique de 3+1 dimensions, les deux classes de théories topologiques ainsi obtenues sont associées à des
configurations de type soit monopole, soit instanton, dont on sait qu’elles jouent un rôle essentiel dans le
mécanisme non perturbatif de confinement de la chromodynamique quantique.
Les questions se posant autour de telles idées sont nombreuses, avant même envisager d’y inclure les
configurations de champs de matière (quarks). Ce programme a donc été attaqué en commençant par les
dimensions les plus petites d’espace-temps, 0+1 et 1+1, pour lesquelles des solutions exactes pour toute valeur
du couplage de jauge peuvent être obtenues. En effet, toute la physique de ces systèmes réside uniquement dans
le secteur des configurations de jauge indépendantes de l’espace, celles dépendantes de l’espace ne représentant
que des degrés de liberté associés à la symétrie de jauge. Ceci fut l’objet essentiellement du travail de DEA de
Joël Martinez-Martinez, et une part du travail actuel de Florian Payen.
En raison de l’importance de ces configurations topologiques, et afin de rendre manifestes toutes les
conséquences de la topologie non seulement dans l’espace-temps mais également dans l’espace des
configurations des champs de jauge, ce programme est poursuivi en prenant comme topologie spatiale celle d’un
tore. Par la même occasion, tout problème de divergence infra-rouge est ainsi sous contrôle. Ceci entraîne la
possibilité de divers choix de conditions au bord pour les champs de jauge, dont la classification complète est en
cours.
L’application de ce programme pour des groupes de Lie compacts abéliens et non abéliens se poursuit, à
commencer par les théories à 2+1 dimensions d’espace-temps. Dans l’avenir, une part importante de ce travail
sera consacrée au cas physique à 3+1 dimensions. Ce programme possède également diverses extensions
potentielles incluant des questions liées à une formulation quantique de l’interaction gravitationnelle, dans le cas
de groupes de Lie non compacts.
[1] E. Witten, Comm. Math. Phys. 117 (1988) 353; ibid 121 (1989) 351.
[2] E. Witten, Nucl. Phys. B311 (1988) 46; ibid B323 (1989) 113.
2.5.3. Nonperturbative approaches to two-dimensional gauge theories
J. Govaerts (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve) ; G.
Avossevou, L. Gouba, M.N. Hounkonnou (Unité de Physique Théorique, Institut de Mathématiques et de
Sciences Physiques, Université d’Abomey-Calavi, Porto-Novo, République du Bénin)
Résumé : L’application du projecteur physique comme technique de quantification de théories de jauge exempte
de toute fixation de jauge, est poursuivie pour des théories de jauge U(1) à 1+1 dimensions. Suite à la
résolution du modèle de Schwinger, des théories avec des champs de matière scalaires sont
maintenant étudiées, en développant les outils nécessaires de fermionisation de ces degrés de liberté
couplés au champ de jauge.
Following the successful application[1,2] of the physical projector approach[3] (which does away with the
necessity of any gauge fixing in the quantisation of gauge invariant systems and thus avoids from the outset any
of the issues surrounding Gribov problems) to the 1+1 dimensional Schwinger model as the example par
excellence of an exact nonperturbative solution to an interacting quantum field theory displaying many of the
features which have to be realised within quantum chromodynamics, we are now pursuing a similar programme
including scalar field degrees of freedom.
Bosonisation of the fermionic degrees of freedom is an essential tool for the solution of the Schwinger
model. Likewise, it should be possible, by fermionising the bosonic degrees of freedom of massless scalar
electrodynamics in 1+1 dimensions, to reach an exact nonperturbative solution of that quantum field theory.
Over the last year, the necessary ingredients for this programme have been developed, starting with the
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fermionisation of a free massless complex scalar field. These results are now being extended to include the
interaction to a U(1) gauge boson.
In the course of this study, we have also explored the potential for a solution to this problem using the
techniques of light-cone quantisation. However, it turned out that because of the masslessness of the degrees of
freedom, extra technical complications render the approach difficult, which is why we returned to a quantisation
based on the instant form of field dynamics. This is also the form of quantisation which sufficed for the exact
solution of the Schwinger model.
Further developments of this programme should include a study of U(1) gauge interactions in 1+1
dimensions coupled to both massless scalar and Dirac degrees of freedom. Ultimately, we are aiming at a
nonperturbative understanding of a supersymmetric version of massless electrodynamics in 1+1 dimensions,
which includes still further interaction terms. Indeed, one intriguing consequence of the bosonisation and
fermionisation procedures employed, is that gauge transformations of the degrees of freedom are then realised
nonlinearly on the transformed variables, whereas they are realised linearly for the original fields. The same
issue should arise for the supersymmetry transformations of the original fields. Such nonlinear realisations of
local symmetries and supersymmetries could possibly be generalised to higher dimensional field theories.
[1] G. Avossevou, Théories de jauge et états physiques à 0+1 et 1+1 dimensions, Ph. D. Thesis, Institut de
Mathématiques et de Sciences Physiques, Université d’Abomey-Calavi (Republic of Benin), April 2002,
unpublished.
[2] G. Avossevou and J. Govaerts, The Schwinger Model and the Physical Projector : a Nonperturbative
Quantization without Gauge Fixing, Proceedings of the Second International Workshop on Contemporary
Problems in Mathematical Physics, October 28 - November 2nd, 2001, Cotonou (Republic of Benin), eds. J.
Govaerts, M.N. Hounkonnou and A.Z. Msezane (World Scientific Publishing, Singapore, 2002), pp. 374394.
[3] J.R. Klauder, Ann. Phys. 254 (1997) 419 ;
J.R. Klauder, Nucl. Phys. B547 (1999) 397 ;
J.R. Klauder, Quantization of Constrained Systems, Lect. Notes Phys. 572 (2001) 143, arXiv :hepth/0003297.
2.5.4. Neutrino pair production in background electromagnetic fields and anomalous
couplings
J. Govaerts, J. El Bachir Mendya) (Institut de Physique Nucléaire, Université Catholique de Louvain, Louvain-laNeuve, Belgium)
Résumé : En continuité avec des études antérieures de propriétés des neutrinos sensibles à la physique au-delà
du Modèle Standard, nous poursuivons notre analyse de la production de paires de neutrinos de
Dirac massifs en présence d’un champ électromagnétique externe au travers de possibles couplages
dipolaires magnétique et électrique anomaux. En l’absence de tels couplages et pour des particules
chargées, ce problème non perturbatif connaît une solution exacte célèbre. Son extension à de tels
couplages anomaux offrirait diverses avenues d’applications physiques intéressantes.
Following the study of a series of neutrino properties in the presence of physics beyond the Standard
Model[1,2], for the first three months of Jean El Bachir Mendy’s postdoctoral stay, we have resumed the analysis
of the possible production of neutrino pairs in a homogeneous electromagnetic background field, in the presence
of both magnetic and electric dipole moments. Even though such couplings are nonrenormalisable in a
fundamental Lagrangian, they are induced through radiative corrections in the presence of physics beyond the
Standard Model for massive Dirac neutrinos and could thus appear in any effective description of neutrino
interactions. In particular, a nonvanishing electric dipole would define a CP violating coupling to the
electromagnetic field.
The solution to this problem for charged massive Dirac fermions, without anomalous couplings, is well
established in the literature, starting with Schwinger’s famous result for electron-positron pair production in a
constant electric field[3]. The coupling to anomalous couplings, on the other hand, is still a widely open problem
in 3+1 dimensions. In 2+1 dimensions, an explicit solution is available however[4]. But so far it has eluded any
extension to 3+1 dimensions, even if only in the presence of a magnetic moment for the neutrino.
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The physics interest of such a result, when achieved, should be clear. Within the context of
astrophysics, there exists situations with extremely large magnetic fields, sufficiently so that a non negligible
amount of power could be radiated in some stellar processes of great interest also through neutrino pair emission
and not only through the electromagnetic spectrum, even for neutrino magnetic moment values less than the
present experimental upper bounds. Also, this process could provide a cheap source of neutrinos, albeit with very
low energies and small production rates. Furthermore, when completed, such a study could be extended to
transition moments both for Dirac as well as Majorana massive neutrinos.
[1] J. El Bachir Mendy, Etude de processus quantiques neutrinos-leptons chargés au-delà du Modèle Standard,
Ph. D. Thesis, Institut de Mathématiques et de Sciences Physiques, Université d’Abomey-Calavi (Republic
of Benin), December 2001, unpublished.
[2] J. El Bachir Mendy and J. Govaerts, A General Effective Four-Fermion Lagrangian for Dirac and Majorana
Neutrino-Charged Matter Interactions, Proceedings of the Second International Workshop on
Contemporary Problems in Mathematical Physics, October 28 - November 2nd, 2001, Cotonou (Republic of
Benin), eds. J. Govaerts, M.N. Hounkonnou and A.Z. Msezane (World Scientific Publishing, Singapore,
2002), pp. 268-289.
[3] J. Schwinger, Phys. Rev. 82 (1951) 664.
[4] Q. Lin, J. Phys. G25 (1999) 17-26 ; ibid 25 (1999) 1793-1795.
a) On postdoctoral leave from the Cheik Anta Diop University, Dakar, Republic of Senegal, on a Fellowship
of the Agence Universitaire de la Francophonie (AUF).
3. HARP: production de hadrons dans les collisions proton-noyau vers
GeV/c
J.S. Graulich, Gh. Grégoire et collaboration HARP (Institut de Physique Nucléaire, Université Catholique de
Abstract : A lot of work has been undertaken to understand and correct the large cross-talk betwwen the TPC
channels. It is now nearly finished. All softwares are being finalized. The final analysis will be
undertaken in Spring 2004.
L'expérience HARP au CERN a terminé l'acquisition à la mi-octobre 2002. L'ensemble du programme
scientifique prévu par la proposition d'expérience a été accompli. La calibration absolue de la réponse du grand
détecteur Cerenkov construit par l'équipe de Louvain a été effectuée à l'aide d'électrons de basse énergie.
L'analyse des résultats recueillis s'est poursuivie durant toute l'année 2003. Un important travail de
préparation à l'analyse a été entrepris pour comprendre et corriger les effets de diaphonie entre canaux du
détecteur TPC. Simultanément tous les sous-détecteurs ont été calibrés et alignés. L'analyse finale de l'ensemble
des données sera entreprise au début 2004.
4. MICE: Muon Ionization Cooling Experiment
Gh. Grégoire (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium) et
collaboration MICE
Abstract: The design of the electron-muon identifier is nearly finalized. In addition we studied and optimised a
soft iron shielding to protect the downstream detectors from the stray magnetic field generated by the
second spectrometer.
Pour mémoire, le groupe de Louvain est responsable de la conception d'un identificateur électron-muon.
Il est constitué d'un grand détecteur Cerenkov basé sur un radiateur en aérogel. L'optique de collection
de la lumière Cerenkov a été optimisée pour atteindre une efficacité de l'ordre de 80 %.
La conception détaillée du dispositif a été poursuivie en 2003 de façon à disposer de l'ensemble en fin
2004 pour les premiers essais en faisceau au Rutherford Appleton Laboratory (RAL). Cet instrument, tout
comme un détecteur à temps de vol et un calorimètre, est situé immédiatement en aval d'un spectromètre à
aimant supraconducteur dont le champ magnétique central est de 4 Tesla.
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Parmi les aspects importants pour le fonctionnement de ces détecteurs, nous avons étudié leur blindage
magnétique contre le champ de fuite du spectromètre. Nos résultats ont été confirmés séparément par le groupe
spécialisé du RAL.
Figure 1 : Schéma de la disposition des détecteurs dans la zone aval de l'expérience MICE.
Les dimensions sont exprimées en millimètres.
Figure 2 : Vues en coupe de l'identificateur électron-muon. Les dimensions sont exprimées
en millimètres.
5. ALEPH
B.Clerbaux (ULB), G. de Hemptinne (FRIA), C. Delaere (FNRS), G. Leibenguth, V. Lemaître (FNRS), O. van
der Aa (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium)
5.1. Charged Higgs searches at ALEPH
G. de Hemptinne (FRIA), V. Lemaître (Institut de Physique Nucléaire, Université catholique de Louvain,
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Résumé : En 2000, la collaboration L3 a publié l’observation d’un excès d’événements par rapport à la
prédiction du Modèle Standard. Cet excès était compatible avec la production d’une paire de Higgs
chargés se désintégrant hadroniquement en un quark c et un quark s. Une analyse semblable a été
reproduite sur les données du détecteur ALEPH à des énergies centre de masse entre 204 et 209 GeV
dans le but de confirmer ou d’infirmer cette observation. Il s’est avéré que le nombre de candidats
observés était conforme à celui attendu dans le cadre du Modèle Standard. En supposant un rapport
d’embranchement hadronique de 100 %, une limite inférieure sur la masse des Higgs chargés a été
obtenue à 95 % de niveau de confiance. La limite observée vaut 75.1 GeV/c2 alors que celle attendue
vaut 74.7 GeV/c2.
In 2000, the L3 collaboration noticed an excess of events with respect to the Standard Model
prediction[1]. This excess was compatible with the production of a pair of charged Higgs bosons at a mass of 70
GeV/c2. The present analysis aimed to reproduce the L3 analysis in the most similar way on the data collected
with the ALEPH detector.
Charged Higgs bosons should be produced at LEP via the process e+e- → Z/γ → H+H-. They are
expected to decay mainly into the heaviest kinematically allowed lepton and its associated neutrino, or into the
heaviest kinematically allowed quark pair whose decay is not Cabibbo-suppressed. Hence, the most important
decay modes at LEP are H+H- → τ ντ τ ντ, τ ντ cs, and cscs. The relative branching ratio is model dependent. The
analysis was restricted to the fully hadronic channel, assuming a 100 % branching ratio.
Hadronic events from H+H- have a high multiplicity and are balanced in transverse and longitudinal
momenta. A large fraction of the centre-of-mass energy is deposited in the detector, typically as four hadronic
jets. Therefore, the most important backgrounds were those presenting a four-jet topology, i.e. the WW- and ZZpair production, decaying into four quarks, and the qq-events from higher order in QCD.
The analysis was performed on e+e- data collected in 2000 with the ALEPH detector (LEP) at centre-ofmass energies between 204 and 209 GeV, corresponding to a luminosity of 213.5 pb-1.
The statistical method is based on the computation of the maximum likelihood ratio for which the
choice of a discriminant variable is needed. The estimated charged Higgs mass was used for this purpose. It was
directly obtained from the jet pairing invariant mass and further improved by means of a five constrains
kinematic fit using the energy-momentum conservation and assuming the equality of the charged Higgs masses.
A set of about 15 variables close to the ones of the L3 analysis was used for selecting the signal. Cuts
were optimized by minimizing the expected confidence level <CLS> at 205 GeV for a Higgs mass of 70 GeV/c2.
Confidence levels were computed for the signal and for the background at 16 mass hypotheses between
60 and 90 GeV/c2, assuming a 100 % branching ratio for the fully hadronic channel. The number of observed
events was consistent with the number of expected events. No indication of pair-produced charged Higgs bosons
was observed. Therefore the L3 observation was not confirmed. Moreover the analysis provided a lower limit of
75.1GeV/c2 on the Higgs mass in the case where B(H→cs)=1 (the corresponding expected limit is 74.7 GeV/c2).
Hence the analysis excluded the presence of a charged Higgs boson at 70 GeV/c2 corresponding to the excess
observed by the L3 collaboration.
[1] L3 collaboration, Phys. Lett. B496 (2000) 34-42.
5.2. Une extension minimale du secteur scalaire: le modèle à un singulet
G. de Hemptinne (FRIA), V. Lemaître (Institut de Physique Nucléaire, Université catholique de Louvain,
Résumé : A minimal extension of the scalar sector is considered, by including one scalar singlet in addition to
the Standard Model doublet. This leads to new theoretical features and experimental signatures.
ALEPH (e+e-, LEP) data are analysed in this context.
Voici déjà une quarantaine d’années que Brout, Englert et Higgs ont introduit l’idée d’un mécanisme de
brisure spontanée de la symétrie de jauge et de génération des masses. Celui-ci est décrit dans le cadre du
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Modèle Standard des interactions fondamentales et nécessite l’introduction d’un doublet de champs scalaires. En
conséquence, si le mécanisme s’avérait correct, un champ scalaire élémentaire devrait être observable.
Alors que toutes les données expérimentales viennent confirmer le Modèle Standard, il n’existe encore à
ce jour aucune évidence de la présence d’une particule scalaire élémentaire. De plus, certains problèmes restent
non résolus dans ce cadre. C’est le cas, par exemple, de l’unification des constantes de couplages et des
problèmes de hiérarchie et de naturalité. En ce sens, on conçoit donc aisément l’intérêt d’étudier des secteurs
scalaires étendus.
Les contraintes expérimentales et esthétiques les plus importantes à ce jour pour étendre le secteur
scalaire incluent la naturalité de ρ=1, l’unification des constantes de couplages et la valeur du rapport
d’embranchement b → sγ. L’extension du secteur scalaire peut amener de nouveaux phénomènes. La possibilité
de violation spontanée de la symétrie CP, l’existence de courants neutres avec changement de saveur, l’existence
du couplage HWZ au tree-level, l’attribution d’une masse de majorana aux neutrinos constituent autant de
motivations théoriques à l’extension du secteur scalaire du Modèle Standard.
Le modèle étudié est une extension minimale du Modèle Standard qui consiste à ajouter un singulet
scalaire complexe au doublet standard. Outre l’invariance sous la symétrie de jauge SU(2)L⊗U(1)Y, le lagrangien
du modèle est supposé posséder une symétrie CP ainsi qu’une symétrie globale U(1) additionnelle correspondant
à la phase du singulet. Lors de la brisure de la symétrie de jauge, les composantes neutres réelles des deux
multiplets se mélangent pour donner deux états scalaires physiques, H1 et H2. Les masses, m1 et m2 de ces
particules, l’angle de mélange δ ainsi que tanβ, défini par le rapport des valeurs dans le vide des deux multiplets,
sont des paramètres libres du modèle . Outre les champs physiques H1 et H2, il subsiste aussi un boson de
Goldstone J issu de la brisure de la symétrie globale additionnelle.
L’analyse utilise des données e+e- collectées en 2000 avec le détecteur ALEPH (LEP) entre 203 et 209
GeV (L ≈ 200 pb-1). Le signal étudié correspond aux processus :
e + e − → Z ∗ → Z (→ νν ) H (→ bb ) et e + e − → Z ∗ → Z (→ qq ) H (→ JJ )
pour lesquels la topologie est composée de deux jets et d’énergie manquante.
Les rapports d’embranchement de ces deux processus dépendent de la valeur des paramètres δ et tanβ.
Pour des valeurs extrêmes de tanβ, il est possible d’isoler les deux processus. Ainsi, seul celui pour lequel le
Higgs se désintègre de manière invisible en deux bosons de Goldstone a été étudié pour le moment.
Des zones d’exclusion ont été obtenues dans le plan (m1, m2) pour différentes valeurs de l’angle de
mélange. Elles sont représentées à la figure 1.
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Figure 1 : Limite conjointe à 95 % de niveau de confiance sur les masses des deux bosons de
Higgs du modèle à un singulet pour différentes valeurs de l’angle de mélange (δ =
5°, 30°, 45°, 60°, 85°). Les zones d’exclusion se situent à gauche des courbes.
5.3. Search for a Higgs boson decaying into W pairs at LEP
C. Delaere (FNRS), V. Lemaître, B. Clerbaux (ULB), O. van der Aa (Institut de Physique Nucléaire, Université
Résumé : La recherche d’un boson de Higgs se désintégrant en paire de boson W en association avec une paire
de fermions a été réalisée au moyen du détecteur ALEPH. L’analyse s’est concentrée sur les données
2000 ou un total de 212.9 pb-1 a été collecté pour des énergies centre-de-masse allant de 205 à 209
GeV. Quatre sélections exclusives sont développées qui correspondent aux différentes topologies.
Une limite supérieure sur le produit de la section efficace the e+ e - → Hff et du branchement du
boson de Higgs en deux W, en fonction de la masse du boson de Higgs, est obtenue.
In the Standard Model (SM), particle masses are generated via the Higgs mechanism implemented using
one doublet of complex scalar field. In this process one physical state remains in the spectrum, known as the
Standard Model Higgs boson. The most important phenomenological consequence of an extended Higgs
structure is the appearance of additional physical spin-0 states. For example, a Higgs model incorporating two
doublets of complex scalar fields generates five scalar Higgs bosons, three of which are neutral. For certain
choices of the model parameters, one of these neutral scalars provides mass only to the fermions and the other
couple exclusively to the bosons, i.e. is a "fermiophobic" Higgs boson. Furthermore, all Higgs models could
display enhanced bosonic couplings due to anomalous couplings in the Higgs sector.
The search for a fermiophobic Higgs boson has been primarily carried out in the two photons channel,
in which the Higgs boson couples to photons via a W loop. For fermiophobic Higgs boson heavier than 90 GeV,
the predicted branching fraction for this channel becomes small relative to the predicted WW branching
fraction (Figure 1) motivating a search in this new channel.
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Figure 1 : Branching fraction in for the higgs into the WW, ZZ and γγ channels.
The main production processes at e+e- colliders for a fermiophobic Higgs boson are e+e- to Z* to hZ
(Higgsstrahlung), WW and ZZ fusion. The cross section for the boson fusion production processes are
considerably smaller than the Higgsstrahlung process for LEP center-of-mass energies.
In the Higgs mass range kinematically accessible for Higgsstrahlung at LEP (mH < 120 GeV/c2), at most
one on-shell W can be produced. Even if the partial differential width of the Higgs boson to WW is dominated
by h to W*W* rather than h to WW*, one of the virtual W's is expected to be near on-shell, and the other to
have a much smaller mass and energy.
The full spectrum of hZ to WW*ff contains a total of 96 different channels depending on the decays of
the W's and the Z. These final states were grouped in 4 exclusive classes depending on the number of hard
leptons in the final state.
The analysis is performed on the data taken in the year 2000 at centre-of-mass energies ranging from
204 to 209GeV.
Four exclusive classes are defined according to the different final state topologies. The first class
contains topologies with no lepton, it is the fully hadronic class. Topologies with more than 1 hard lepton are
taken in the second class. The third and the fourth classes contain topologies with one hard lepton, and one soft
lepton, respectively. For each class, the numbers of candidate events observed in the data and those expected
from SM background processes are given in Table 1. The expected number of events from a 110 GeV Higgs
boson decaying exclusively into WW is also given.
Table 1 :
The third column shows the number of expected events after the analysis with the
observed number of events.
97
Following the LEP Higgs working group method, the 4 channels are combined using the frequentist
confidence level presented in [1] and implemented within the ROOT package [1].
From the full data sample, a 95 % C.L. upper limit on the number of signal events at a given invariant
mass is derived. The resulting 95 %C.L. upper limit is shown on Figure 2.
Figure 2 : Limit on ξ2 as a function of the Higgs boson mass.ξ2 = B(H → WW)σ(e+e-→
Hff)/σsm(e+e-→ Hff).
The presence of any Higgs boson decaying exclusively to two (virtual) W bosons cannot be excluded in
the context of this analysis (Figure 2) alone. No limit can be put either in the fermiophobic Higgs scenario or in
the BR = 1 case.
Nevertheless, the present analysis extends the reach of the analysis performed by the ALEPH
collaboration in the two photons channel and combination will push the limit obtained.
[1] T. Junk, Nucl. Instrum. and Methods A434 (1999) 435.
[2] René Brun and Fons Rademakers, “ROOT - An Object Oriented Data Analysis Framework”, Proceedings
AIHENP’96 Workshop, Lausanne, Sep. 1996, Nucl. Instrum. and Methods A389 (1997) 81-86. See also
http://root.cern.ch/.
5.4. Granting the access to ALEPH data for the futur
C. Delaere (FNRS), V. Lemaître (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-laNeuve, Belgium)
Résumé : Le stockage à long terme des données d’ALEPH est envisage. Une solution utilisant une base de
donnée orienté objet ROOT est présenté.
The ALEPH database is a BOS database formatted with the EPIO package, based on a FORTRAN
technology. Even if that technology has successfully serviced the collaboration during 10 years of running, and
will be available for several additional years, it is interesting to look for an alternative solution for a longer term
storage and archiving.
ROOT is the solution adopted by the LHC and will be maintained during 10 to 20 years at least. This is
why one has imagined converting the ALEPH database to ROOT files.
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This solution has already been presented in the 2002 CYCLONE report and will therefore not be
discussed again. During the year 2003, several improvements have been implemented into the prototype in order
to enhance the performances, both for speed and disk occupancy. The event size has been strongly reduced to
about 36kB per Monte Carlo event and 1.5 kB for data events. This is about 1.5 times the original size, but
contain additional metadata, so that the new database can be read without specialized software.
At the same time, the conversion time has been kept low – around 70 ms/event – meaning that the full
ALEPH database can be converted in less than 6 month with a single computer.
The actual conversion of the database is being investigated by the ALEPH collaboration.
6. RD39 collaboration
O. Militaru, K. Piotrzkowski, X. Rouby (Institut de Physique Nucléaire, Université catholique de Louvain,
Measurements of forward protons at the LHC pose a big experimental challenge due to very high event
rates, huge background fluences reaching 1015 p/cm2 and a very close distance to the circulating proton beams.
This requires a novel approach to the design of the forward proton tracking detectors.
The deterioration of charge collection efficiency (CCE) due to the trapping of charge carriers is a
critical obstacle for the use of silicon µstrip sensors as detection elements. The heavy irradiation induces deep
defect levels in the silicon leading to the reduction of the signal produced by high energy ionizing particles. A
solution is proposed by the RD39 collaboration to control the detector electric field by filling the trapping levels
in forward current injection mode using p+/n/n+ junction structure operated at forward bias voltage at cryogenic
temperatures [1].
Figure 1 : A photograph of a baby CMS sensor cut along its border strip (the
strip pitch is 120 µm).
When an experiment requires silicon µstrip detectors as close as possible to the beam, the insensitive
area around the strips should be minimized. At the LHC, a forward detector will be placed at a 1.5−2 mm
distance from the beam, therefore to avoid large acceptance losses it should be fully sensitive at the less than 0.5
mm distance from its mechanical edge. The first prototype of such an edgeless module is under construction at
FYNU and CERN. For this purpose, silicon µstrip single sided detectors were chosen (the so-called babydetectors of CMS design), fabricated on a 320 µm thick n-type silicon substrate. These sensors have 196 parallel
strips at 120 µm pitch. The sensors surface is 2.5 cm × 2.0 cm. They were cut in two ways (at the BNL, USA):
with a straight cut along the border strip, (see Figure 1), and with the cut at a small angle with respect to the
strips.
99
At room temperatures such cut sensors cannot be successfully operated because of excessively large
surface currents flowing through a cut edge once the sensor is biased. This results in a large leakage current at
the input of a pre-amplifier, and finally in a large noise. One possibility of decreasing the surface current is
followed at the BNL using a chemical etching of the cut edge. Another possibility of reducing this current at low
temperatures has been studied at FYNU. First, preliminary results shown in Figure 2 indicate that indeed the
leakage current sharply drops with temperature and already at temperatures below –50 °C could be tolerable.
Further such tests at FYNU are in progress.
Figure 2 : Total leakage currents of cut sensors as a function of the
bias voltage at two temperatures of −10 °C and –50 °C.
Prototyping of a first detector module is underway and a sketch of such a module is shown in Figure 3.
It shows layout of the cut silicon sensors, the scheme of cooling using special micro-pipes developed by RD39,
and the way of connecting the readout hybrid circuits of the CMS tracker.
Figure 3 : Sketch of a detector modul with four cut sensors readout by a
CMS hybrid.
Finally, to operate successfully the silicon detectors in cryogenic conditions, the CMS tracker front-end
hybrids, with APV25 chips, have to be tested and tuned to work at these conditions.
100
Figure 4 : Evolution of the APV test signals as a function of the hybrid temperature. Vertical
axis shows the signal amplitude and horizontal one time in ns.
Preliminary tests have been performed using a FYNU CMS module test stand. These preliminary tests
of a CMS hybrid cooled down to about –50 °C show interesting results, like faster signal, higher gain (see Figure
4), and a constant noise level, leading to a better signal-to-noise ratio (for a bare hybrid, without a connected
sensor). More detailed tests at much lower temperatures and full characterizations will be performed, both on the
hybrids and on the edgeless detectors.
First prototype of fully operational detectors are expected in coming months, allowing for a full proofof-principle by measuring its performance at a test beam and using other techniques to induce the signal (like
laser pulses).
[1] O. Militaru, K. Piotrzkowski, X. Rouby et la Collaboration RD39, « RD39 status report », CERN-LHCC2003-060.
7. ZEUS collaboration
Jérôme de Favereau (FRIA), Krzysztof Piotrzkowski (Institut de Physique Nucléaire, Université catholique de
In January 2003 this two-person team joined officially the ZEUS collaboration to make the experiments
at the unique electron-proton collider HERA at DESY. At HERA the polarized electron or positron beams of
27.5 GeV collide with the 920 GeV proton beams. Our scientific interest in ZEUS is directly related to the
investigation of the electro-weak processes in photoproduction with CMS at the LHC. In particular, at HERA we
investigate a very similar process of photoproduction of W bosons in ep collisions, see Figure 1. Later, we would
like also to search for an anomalous production of the top quark and isolated leptons at HERA.
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Figure 1 : A diagram corresponding to the photoproduction of single W bosons at HERA; in this case involving one of
the fundamental features of the Standard Model − the tri-linear gauge coupling γWW. On the right, a
selected candidate for the event ep → eW (→ eν) X, where an electron from the W decay is clearly
identified in the barrel part of ZEUS, and the ‘recoiling’ jet is not balancing the electron transverse
momentum due to the neutrino from W decay which escaped detection.
J. de Favereau performed first search for the W boson candidates, decaying into eν, in the ZEUS data
taken during high luminosity running in 1999 and 2000. He showed to the High Q2 physics group in ZEUS first
results of his analysis in fall 2003. He was encouraged to continue by including also the muon decay channel,
and by correcting for the detector effects and backgrounds using the detailed Monte Carlo simulations. Finally,
he will compare the results with the SM predictions and prepare these results for the ZEUS presentations at
conferences in 2004.
In addition to the physics studies we were involved into the assembly and commissioning of a new
ZEUS component – the 6m tagger, see Figure 2. This small calorimeter detects, at about 6m from the interaction
point, electrons which lost, in an interaction with a proton, a large fraction of the initial energy but were scattered
at very small angles. Therefore, effectively it serves as a photoproduction tagger in the ZEUS experiment, hence
its name. In addition, it serves as a crucial component of the luminosity monitor in ZEUS, because it is also
capable to tag ep bremsstrahlung events used for the precise HERA luminosity measurements.
Figure 2 : The front face of the 6m tagger – a tungsten/scintillator spaghetti calorimeter. On
the right photo, the destroyed by corrosion tungsten plates are shown.
First prototype of this detector failed to operate properly due to a small water leak in its vicinity
followed by a very serious damage of the detector parts. In particular, some tungsten plates were completely
102
destroyed, and in addition most of the scintillating fibers were stained by the water sediments. We participated in
the repair the tagger, in polishing the fibers, in the assembly of the detector and its subsequent tests. The detector
was then successfully installed in July 2003, and is in the routine use since the beginning of 2004. We continue
to participate in its maintenance, in particular by developing the online detector monitoring software.
8. Precision Measurement of Singlet µp Capture in Hydrogen – PSI
Experiment R-97-05
V.A. Andreev, A.A. Fetisov, V.A. Ganzha, V.I. Jatsoura, A.G. Krivshich, E.M. Maev, O.E. Maev, G.E. Petrov,
S. Sadetnsky, G.N. Schapkin, G.G. Semenchuk, M. Soroka, A.A. Vorobyov (St.-Petersburg Nuclear Physics
Institute (PNPI), Gatchina 188350, Russia), P.U. Dick, A. Dijksman, J. Egger, D. Fahrni, M. Hiltebrandt, A.
Hofer, L. Meier, C. Petitjean, R. Schmidt (Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland), T.I.
Banks, T.A. Case, K.M. Crowe, S.J. Freedman, B. Lauss (University of California Berkeley and Lawrence
Berkeley Laboratory, Berkeley, USA), K.D. Chitwood, S. Clayton, P. Debevec, F.E. Gray, D.W. Hertzog, P.
Kammel, B. Kiburg, R. McNabb, F. Mulhauser, C.J.G. Onderwater, C. Ozben, C. C. Polly, A. Sharp, D. Webber
(University of Illinois at Urbana-Champaign, Urbana, USA), L. Bonnet, J. Deutsch, J. Govaerts, D. Michotte, R.
Prieels (Institut de Physique Nucléaire, Université catholique de Louvain, Louvain-la-Neuve, Belgium), T.
Gorringe, M. Ojha, P. Zolnierzcuk (University of Kentucky, Lexington, USA), F.J. Hartmann (Technichal
University of Munich, D-85747 Garching, Germany); R.M. Carey, J. Paley (Boston University, Boston, USA)
Résumé : L’expérience MuCap a pour objectif la mesure du facteur de forme pseudoscalaire induit gp avec une
précision relative de 1 %. Le principe de la mesure repose sur la mesure du taux de capture de µ- sur
le proton dans le système pµ à l’état singlet. Ce taux de capture est évalué par la différence des temps
de vie du µ+ et du µ- arrêtés dans un gaz de protium à une pression de 10 atm. Ce rapport décrit
l’état d’avancement des différents composants du dispositif expérimental et leur certification lors
d’une mesure test réalisée fin 2003.
Figure 1 : MuCap detector with TPC vessel retracted for preparing new protium filling. It is
installed in the MUE4 line of the PSI experimental areas. Pions produced by 600
MeV accelerated protons bombarding the carbon target, decay inflight and
selection of them arrive from the left with a low momentum of 43,3 Mev/c in the
experimental setup.
8.1. Overview
The MuCap experiment [1] is a high-precision measurement of the rate for the basic electroweak process
of muon capture,
µ+p→n+ν
103
(1)
This measurement determines the least well-known of the nucleon charged current form factors, the
induced pseudoscalar gp, to 7 %. MuCap employs a new method that avoids key uncertainties of earlier
measurements. The capture rate is derived from the lifetime difference of positive and negative muons stopped in
an ultra-pure and active hydrogen target (the time projection chamber).
Figure 2 : Side view of the MuCap detector setup.
The main MuCap detector components are depicted in Fig. 2. This is a complex experiment that
imposes stringent requirements on the various subsystems: beam, beam detectors, time-projection chamber
(TPC) and hydrogen vessel (H2), electron detection system (ePC1, ePC2, eSC), gas system and diagnostics,
magnet and data acquisition. All of these components must work flawlessly for the final production run.
8.2. Progress 2003
The main goal in 2003 was to get all essential parts of the MuCap detector functional, commission
them, and prove their performance in a first physics run. This ambitious program was achieved in a sequence of
milestones :
• The time projection chamber (TPC) was commissioned in the µE4 beam during summer 2003. Its primary
purpose is to detect incoming muon tracks and stops. A totally new wire chamber technology was developed
for operation in ultra-clean hydrogen at a pressure of 10 bar. Only UHV-proof bakeable materials like metals,
glass, and ceramics were chosen. Special frames from polished borofloat glass with a low thermal expansion
coefficient were manufactured with metallic coatings onto which the tungsten-gold wires were soldered. The
principal difficulty was to get enough amplification to observe charges drifting in the pure H2 gas. Such high
amplification requires voltages (4.8 kV) significantly exceeding those reached in conventional wire
chambers.
• Deuterium-depleted hydrogen (“protium”) gas of the highest purity had to be produced and maintained
within the TPC pressure vessel. This purity was achieved by high-vacuum baking of the entire TPC cylinder
vessel at 120° C and by filling the protium gas through a palladium filter. In September 2003 we suppressed
the impurity level to ~ 10-7
• The electron detector worked reliably at full operating conditions. It consisted of two parts: the "epC1", a
cylindrical multiwire chamber instrumented with new low-noise, chamber-mounted, front-end electronics,
and the "eSC", a brand-new, segmented, double-layer plastic hodoscope surrounding the wire chambers. All
electron detectors are fastened to the new support structure. In 2004 a second cylindrical wire chamber
"ePC2" will be added, allowing for electron tracking to the muon stop location. The muon and electron
detector groups operate independently, recording the muon lifetime measurement’s start and stop signals as
separate systems. This independence is absolutely essential, because any systematic correlations between the
muon and electron time measurements could induce lifetime curve distortions.
104
• At the beam entrance a muon detection and tracking geometry was commissioned consisting of a thin
scintillator, a collimator, and two wire chamber assemblies. The first wire chamber is outside of the TPC
vessel, while the second sits inside in front of the TPC, surrounded by the protium gas.
• A µSR magnet was placed closely around the TPC pressure vessel providing a vertical magnetic field of ~ 50
Gauss. This field is necessary to control the spin effects of the polarized µ+, and thereby perform checks and
calibration of the lifetime measurement.
• New data compressor units were commissioned to continuously read out the electron chamber signals in a
deadtime-free manner.
• We developed new data acquisition (DAQ) software capable of efficiently handling the data flow of ~ 4
MB/s. The DAQ is a Linux-based system integrated in the MIDAS framework. Stable collection and storage
of 6 TByte of data to the PSI archive and a tape robot system was achieved.
8.3. Commissioning Run
Figure 3 : Total integrated statistics of µ- (solid) and µ+ (dashed) data vs. time,
spanning the period September 12 – October 14, 2003. Only events with
fully functional readout electronics and (in the case of the µ-)sufficiently
clean protium have been included. The blue lines illustrate the integrated
number of entrance muons as recorded by the µSC detector, ending in a
total of 12 x 109 for the µ+ and 3.7 x 109 for the µ+. The red line illustrates
the accumulation of 0.5 x 109 total µ- decay events and 0.2 x 109 µ+,
identification of which involves all detectors.
In September 2003 all of these components were ready for the first commissioning run. After the
replacement of a defective Pd filter, we collected roughly two weeks of µ- data, or approximately 109events. This
represents about 10 % of the statistics needed to reach our final goal, a µp singlet capture rate with 1 % statistical
error. The present data already matches the statistics of previous experiments in this field, but the MuCap
measurement is cleaner because ambiguities in the interpretation (due to ortho-para conversion of ppµ
molecules) are dramatically reduced at our low target density.
The statistics accumulation during this last phase of the run is summarized in Fig. 3. During the final
days of the run we directly calibrated the impurity effect in our data by filling the TPC with protium containing a
controlled impurity admixture of ~ 20 ppm N2.
105
8.3.1. Hydrogen system
After the extended R&D period (1998 - 2000) using standard chamber materials, this run was the first to
prove the functionality of hydrogen chambers constructed exclusively from bakeable high-purity materials.
Fig. 4 shows the impurity level as a function of time, as monitored by reactions such as
µ + N → C* + ν.
(2)
The TPC can detect recoil nuclei (200-350 keV energy) with nearly 100 % efficiency, considering both
solid angle and threshold effects. The background to this method is naturally estimated from µ+ data and found to
be negligible down to impurity levels of 0.01 ppm. The information is collected both from the digital high-rate
TPC readout and from 16 TPC anodes which are also instrumented with flash ADCs. Specialized triggers were
implemented to selectively collect impurity events with the slower flash ADC system.
Figure 4 : The gradual increase in the impurity level with time is plotted above, in the
hours following the September 25 clean filling (blue) and the October 2
clean filling (red). This information was derived in-situ by monitoring
capture events with the flash ADC system and calibrated by gas
chromatography of a sample taken on October 1 (point with open circle).
These results demonstrate that our current hydrogen system permits a purity close to 0.1 ppm, a level at
which it is possible to compute a small correction based on the observed impurity capture events. Most
importantly, the observed initial and outgasing levels are compatible with the capabilities of the continuous
purification system under construction at PNPI, which will lower the impurity level of our system to ~ 0.01 ppm.
The final MuCap system also requires isotopically pure protium, with ≤ 1 ppm deuterium. The
measurement of such low deuterium levels is challenging. Protium samples from MuCap were analyzed at the
Ioffe Institute (St. Petersburg), PSI (Institute for Atmospheric Physics), and the AMS facility of ETH Zürich.
Initial results indicate the protium generated from isotopically pure water has the required purity, while the
sample at the end of the 2003 run has accumulated a few ppm of deuterium. This deuterium contamination may
have been introduced by insufficient purging of the replacement palladium filter.
8.3.2. Detectors and DAQ
The electron detector ePC1 was fully operational. In particular, considering its previous susceptibility to
noise, chamber ePC1 performed exceptionally well by operating quietly and reliably over the entire run. This
improvement in performance was achieved by improved grounding and by placing all digitizing electronics
(compressors) in close proximity to ePC1, on the detector support platform.
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8.3.3. Data analysis and first results
Figure 5 : Top: µ- decay time spectra for each full electron detector: ePC1 and
eSC in coincidence, ePC1 Anodes only, and eSC only. These data are
from the last clean H2 filling with a µ- beam, and they represent only
part of the statistics available. Bottom: residuals from a simple
exponential plus background fit to the data set from the full electron
detector.
Figure 6 : Top: fit results to decay time spectra from individual eSC hodoscope
segments in coincidence with ePC1. The data set used is the same as
in Figure 5 and Table 1. Bottom: accidentals fraction from the time
spectra.
e-Detector
Full
ESC
EPC1 Anodes
Tableau 1 :
Number of e in Fit
2.28 x 108
2.77 x 108
3.57 x 108
δλfit/λfit
8.8 x 10-5
9.1 x 10-5
8.1 x 10-5
λfit/λfit,Full
1
1.000050
1.000021
Accidentals Fraction
1.18 x 10-3
8.43 x 10-3
5.74 x 10-3
µ- decay rate λfit found for each electron detector used, normalized to λfit,Full of the full electron
detector (ePC1 anodes, ePC1 inner cathodes, ePC1 outer cathodes, and eSC, all in coincidence).
Fig. 5 shows µ- lifetime results for data from the last clean fill, taken October 2 – 8. The analysis is
based on so-called global pileup protection, wherein we only consider entrance muon candidates that are isolated
in time by at least 25 µs. While this approach results in a significant reduction of the statistics, it safely avoids
problems which arise from mistakenly associating uncorrelated muons and decay electrons. A simple fit to a
function containing an exponential decay and a uniform background describes the data well at this level of
statistics, which is approximately half of the total available from the clean protium runs. The rest of the clean
protium data will be included as the analysis software is further refined. The fit parameter values are summarized
107
in Table 1. Lifetime results are given in relative units, as the analysis is currently performed in a blind, unbiased
mode, with the accurate time calibration unknown to the analysis team. The consistency of the ePC results with
the simpler eSC scintillators is especially encouraging, as the experience of precision lifetime experiments with
wire chambers is quite limited.
Comparison of lifetimes and background levels extracted from individual electron detector segments
indicates that the detectors are functioning properly, and illustrates the possibilities for reducing accidental
background. As can be seen in Fig. 6, the fit results and accidentals fractions1 are consistent. Using the full
electron detector–that is, including both eSC layers and ePC1 anodes and cathodes–the accidentals level is
~ 10-3. We expect an order-of-magnitude improvement when the new ePC2 is in place, as it will allow
backtracking to the muon stop location in the TPC.
[1] http://www.npl.uiuc.edu/exp/muoncapture/
1
Defined as the level of the flat part divided by the peak of the decay-time histogram.
108
III. INSTRUMENTATION ET DÉVELOPPEMENTS TECHNIQUES
1. On-line results with LISOL laser ion source
Yu. Kudryavtsev, P.Van den Bergh, J. Gentens, M. Facina, M. Huyse, P. Van Duppen (Katholieke Universiteit
Leuven, Instituut voor Kern -en Stralingsfysica, Belgium 3001)
Résumé : Des études sous faisceau ont permis de tester l’utilisation d’une enceinte gazeuse remplie d’un gaz
noble (argon) afin de thermaliser, de stocker et de transporter des atomes et des ions radioactifs
présents à l’état de traces. Aprés thermalisation dans un gaz noble sous haute pression, des ions
radioactifs produits lors de réactions nucléaires ainsi que des ions stables de grande énergie
cinétique issus d’un cyclotron ont été ré-ionisés de manière sélective par un laser au moyen d’un
processus résonant en deux étapes. L’efficacité de conversion de la source d’ion laser d’un faisceaux
d’ions stables et trés énergétiques en un faisceau de basse énergie est donnée.
1.1. Introduction
A gas cell filled with noble gas can be used to stop nuclear reaction products from heavy-ion fusion
after an in-flight separator. In this way, high-energetic beams with large divergence can be converted into a low
energetic one for precision experiments or for the consequent injection into a post-accelerator. This concept is
considered nowadays within different existing and new projects [1]. The ions are guided towards the exit hole of
the gas cell by the combination of DC and AC electric fields. Since also the secondary beam induces a high
degree of ionization of the buffer gas, the intensity of the outgoing radioactive beam could be limited by space
charge effects inside the cell [2]. On expense of evacuation time, much higher intensities can by obtained by using
laser ionization in the gas cell. The laser ion source at LISOL (Leuven Isotope Separator On-Line) [3] and
references therein] has been used already during many years to study exotic nuclei far from stability. These
nuclei were produced in heavy ion induced fusion or proton induced fission reactions. At on-line conditions a
high ion-electron density is created by the primary particle beam and by the slowing down of the radioactive ions
created in the nuclear reaction. This causes additional recombination losses of laser-produced ions. Furthermore
ionization of the buffer gas also leads to more complicated chemical reactions of impurity molecules with beamcreated ions [4]. The interactions of ions with impurity molecules, with noble gas atoms, with electrons and with
electrical fields have been investigated in order to specify the requirements for the gas cell as a source of
radioactive rare isotopes for the next generation radioactive ion beam facilities [5].
1.2. Experiments with stable 58Ni beam
In order to get a more quantitative idea of the performance of the laser ion source, a 185 MeV 58Ni
beam from the cyclotron accelerator has been used. The energy of the beam was chosen in such a way that after
passing two molybdenum windows (4.1 µm and 4.37 µm thick) the 58Ni ions are stopped in the middle of the gas
cell when filled with 500 mbar of argon. The energy of the beam after the cell entrance window is 26 MeV. The
position of the stopped nickel ions is very well localized. The cyclotron beam has a diameter of about 6 mm and
the longitudinal straggling due to the stopping is about 3 mm.
The most important parameters of the laser ion source are the efficiency and selectivity. The efficiency
is defined as the ratio of the number of mass separated ions to the number of ions entering the stopping volume
of the gas cell. As such the transport efficiency of the SPIG [6] and the mass separator are also included in the
definition. The selectivity of the laser ion source is defined as the number of ions of a specific element in the
mass-separated beam when the lasers are tuned on resonance to the number of ions of that element in the massseparated beam when the lasers are off. In some circumstances the total current coming out of the gas cell can
also be important; this current will mainly consist of buffer gas ions and ionized impurities.
The ions created by the stopping of the 58Ni beam and eventually flowing out of the gas cell can be mass
analyzed. The mass-analyzed ion current has been investigated in a wide range of primary beam current. Figure
1 gives the efficiency of the gas cell and mass separator for transporting beam and/or laser created ions from
their production point in the gas cell to the focal plane of the separator. The experimental data were collected
during 192 beam-hours using different configurations. The cyclotron beam intensity was controlled by varying
the cyclotron settings and when at the lower intensity side unstable conditions were met by introducing
mechanical grids. The cyclotron beam intensity was monitored in the high intensity domain with a Faraday cage
109
and in the low intensity domain with a plastic scintillator. The mass-separator intensity was measured in the high
intensity domain with a Faraday cage and in the low intensity domain with a Secondary Electron Multiplier.
Special care was taken to intercalibrate the different gauges.
Part of the results of measurements are displayed in Figure 1. When the initial Ni beam intensity is as
low as 1 particle per second more than 10 % of the created Ar ions (one 26 MeV Ni stopped in Ar creates ~ 106
ion-electron pairs) are collected. This efficiency steeply decreases when the beam intensity increases and finally
levels off at 10-5 %. Measuring mass-separated Ni ions to very low intensities is harder than for Ar ions as the
charge-creating multiplication factor is not present. At primary Ni intensities around 104 pps, an efficiency
around 10 % is observed. This number is not sensitive to the fact if the lasers are on (squares) or off (circles).
Increasing the intensity also decreases the efficiency of collecting the non-resonant Ni ions (those Ni ions which
are in ionic state after thermalization in the gas cell and during transport in the gas cell). The efficiency levels off
to ~ 0.02 %. The Ni ions re-ionized by laser light do show a less dramatic behavior as a function of the beam
intensity although the efficiency also drops to reach a 1 % level. The difference in behavior between nonresonant Ni ions and laser-produced ions results also in a change in selectivity from 1 around 104 pps over 100
around 107 pps to 50 at the highest intensities. The fact that around 104 pps no enhancement is observed with
lasers on resonance means that the number of neutral Ni atoms in their atomic ground state and available for
laser ionization is small compared to surviving Ni ions. The big difference in efficiency between Ar and nonresonant Ni ions is striking. This is probably due to the difference in ion-electron density in the ion track region,
where most of the Ar ions are created, and the stopping region where the Ni ends up. According to SRIM
calculations [7], the ion-electron density is 10 times lower at the end of the Ni ion’s track (i.e. in the place where
the Ni ion stops) compared to the beginning of the Ni ion’s track inside the gas cell. Furthermore the energy of
the Ni beam was chosen such that ions are stopped in the middle of the cell. The gas flow there is faster than in
the regions closer to the wall.
Apart from the efficiency measurements, time profiles and the influence of AC and DC electrical fields
have been measured. Furthermore, careful laser ion source efficiency measurements for heavy-ion fusionevaporation reactions have been performed. These resulted in 12% efficiency for the 58Ni (40Ar, 2n 1p) 95Rh.
Figure 1 : Efficiency of the LIS for extraction of 58Ni ions with lasers-on, and lasers-off
respectively, and for extraction of 40Ar ions, as function of the implanted beam
current into the gas cell.
[1] Proceedings of the 14th International Conference on Electromagnetic Isotope Separators and Techniques
Related to their Applications, Nucl. Instrum. and Meth. in Phys. Res. B204 (2003) 1-821.
[2] M. Huyse et al., Nucl. Instrum. and Meth. in Phys. Res. B187 (2002) 535-547.
[3] Yu. Kudryavtsev et al., Nucl. Instrum. and Meth. in Phys. Res. B179 (2001) 412-435.
[4] Yu. Kudryavtsev et al., Nucl. Instrum. and Meth. in Phys. Res. B204 (2003) 336-342.
[5] M. Facina et al., to be submitted to NIM B.
[6] P. Van Den Bergh et al., Nucl. Instrum. and Meth. in Phys. Res. B126 (1997) 194-197.
[7] http://www.srim.org
110
IV. EXPLOITATION ET DÉVELOPPEMENTS DES CYCLOTRONS
Résumé : Un nombre record d’heures de faisceaux radioactifs a été produit cette année. Alors que la moyenne
sur les cinq dernières années se situe aux environs de 700 heures, 1207 heures ont été délivrées sur
cible, utilisant CYCLONE110 et CYCLONE44 comme post-accélérateurs. Depuis le premier faisceau
radioactif en 1989, nous totalisons ainsi plus de 10.000 heures sur cible. Sept isotopes radioactifs
différents ont été accélérés cette année : 6He, 7Be, 10C, 15O, 18F, 18Ne et 19Ne.
Les travaux de physique réalisés en 2003 ont donné lieu à des résultats intéressants. Mentionnons
notamment :
En physique nucléaire, de nouvelles informations ont été obtenues sur la spectroscopie des noyaux
légers (5H, 6He, 7He, 11N, 19Ne) qui ont été produits dans des réactions induites par des faisceaux
radioactifs ; d’autre part, la structure nucléaire des isotopes Ni et Co a été étudiée après production
par une source d’ions laser.
En astrophysique nucléaire, deux réactions induites par des faisceaux radioactifs ont été mesurées :
18
F(α,p)21Na et 19Ne(p,γ)20Na ; la première est active dans une chaîne susceptible de produire des
neutrons déclenchant le processus-r, alors que la deuxième procède du cycle CNO-chaud.
Les faisceaux de 10C (T1/2 = 19.3 s) et de 15O (T1/2 = 2 min) ont été utilisés pour la première fois
pour des expériences.
Le transfert du système de contrôle de CYCLONE44 de Coros vers WinnCC et l'intégration des sousensembles qui sont encore commandés localement a bien progressé. Un nouveau cocktail d'ions
lourds avec un M/Q voisin de 3.3 a été mis au point sur la source ECR SCAMPI.
1. INTRODUCTION
This year a record amount of hours of radioactive beams has been produced. While the average over
the past five years is about 700 hours, 1207 hours have been delivered on target, using respectively
CYCLONE110 and CYCLONE44 as post-accelerator. Since the first radioactive beam in 1989, we totalize
more than 10.000 hours of beam on target. This year, seven different radioactive isotopes have been
accelerated : 6He, 7Be, 10C, 15O, 18F, 18Ne and 19Ne.
The physics experiments realized in 2003 have given interesting results. We can mention :
-
In nuclear physics, new information has been obtained about the spectroscopy of light nuclei (5H, 6He, 7He,
11
N, 19Ne) which have been produced in reactions induced by radioactive beams ; moreover, the nuclear
structure of the isotopes Ni and Co has been studied after production by a laser ion source.
-
In nuclear astrophysics, two reactions induced by radioactive beams have been measured : 18F(α,p)21Na and
19
Ne(p,γ)20Na ; the first one is active in a chain which may produce neutrons activating the r-process while
the second proceeds from the hot CNO cycle.
2. OPERATION
Statistics on the allocation of beam time in 2003 from CYCLONE110, CYCLONE30, CYCLONE44
and the ECR-source "SCAMPI" are given in Tables 1 to 4.
Physics :
using light ions
heavy ions
radioactive ions
Technological and
radiobiological applications
Accelerator development
Maintenance
Unscheduled shutdown
Hours
1355
%
37.8
1504
41.9
242
409
76
3586
6.7
11.4
2.1
100.0
164
346
845
Table 1 : Beam time delivered by CYCLONE110 in 2003.
111
Hours
1323
1012
2335
Isotope production for PET
Isotope production for RIB
Hours
511
164
675
Physics
Beam developments
Hours
As Injector into CYCLONE110 :
- Physics + Accelerator Developments
- Technological applications
Stand alone :
- Test-runs and conditioning after exchange
of plasma chambers
- Source developments
Unscheduled shutdown
374
763
903
236
54
2330
Table 4 : Operating time distribution of the ECR-source « SCAMPI » in 2003 including
source conditioning and beam optimisation.
The lists of ions accelerated by CYCLONE110 and by CYCLONE44 during the year 2003 are given in
Tables 5 and 6.
Particle
Protons
Deuterons
3
Helium+1
*6Helium+1
*6Helium+2
*7Beryllium+1
*10Carbon+2
*14Nitrogen+2
*15Nitrogen+2
15
Oxygen+2
18
Oxygen+2
18 2+
F
*18Neon+2
*18Neon+4
36
Argon+8
36
Argon+10
40
Argon+8
40
Argon+9
40
Argon+11
39
Potassium+8
58
Nickel+10
132
Xenon+26
**A/Q = 5
***A/Q = 3.33
Hours
647
304
9
130
168
57
164
10
57
129
37
108
24
176
9
85
27
251
94
32
78
9
460
36
3101
%
20.9
9.8
0.3
4.2
5.4
1.8
5.3
0.4
1.8
4.2
1.3
3.5
0.8
5.7
0.3
2.8
0.9
8.1
3.1
1.1
2.6
0.3
14.2
1.2
100.0
Table 5 : List of ions accelerated by CYCLONE110 in 2003.
* = radioactive ion
** = "ion cocktail" : 10B2+, 15N3+, 20Ne4+, 40Ar+8, 84Kr+17, 132Xe+26
*** = "ion cocktail" : 13C4+, 22Ne6+, 28Si8+, 40Ar12+, 58Ni17+, 83Kr25+
112
Particle
Helium1+
14
Nitrogen2+
14
Nitrogen2+
14
Nitrogen2+
19
Fluor3+
19
Fluor3+
19
Fluor3+
19
* Neon3+
20
Neon3+
23
Sodium3+
4
Energy (MeV)
[1]
5.74
6.5
10.0
9.8
10.2
13.2
10.2
10.0
9.4
TOTAL
Hours
111
46
9
9
103
16
123
195
7
43
662
Table 6 : List of ions accelerated by CYCLONE44 in 2003.
[1] for helium implanted target fabrication – at variable source voltage
*
radioactive ion
The list of physics experiments which received beam time in 2003 is given in Table 7.
PH-177
PH-184
PH-196
PH-197
PH-198
PH-199
PH-200
PH-204
PH-205
PH-206
DT-
Beta-decay of neutron deficient nuclei below 100Sn
(KULeuven – GSI Darmstadt – Univ. Edinburgh)
The 18F(α,p)21Ne reaction : a key to understanding
neutron production in r-process sites (Univ. York –
Univ. Edinburgh – UCL – Univ. Notre Dame –
TRIUMF)
Measurement of the 6He → α + d + e- + ν branching
ratio (KULeuven – CEA Saclay – UCL)
Spectroscopy of 19Na by elastic and inelastic
scattering of a 18Ne beam on a proton rich target (UCL
– ULB – Univ. Edinburgh – Univ. Connecticut –
GANIL – LPC Caen)
Study of 11N using 10C + p scattering (UCL – Univ.
Edinburgh – ULB – Univ. Connecticut)
Investigation of resonances in 7He using the
9
Be(6He,8Be)7He reaction (UCL – CEA Saclay –
FLNR Dubna – INFN Catania – ULB)
A systematic study of the 39K background from ECR
sources – a crucial step in developing an AMS
detection method for natural 39Ar (Univ. Wien –
Columbia Univ. – Argonne Nat. Lab. – UCL –
Hebrew Univ. Jerusalem)
Nuclear structure studies of neutron-rich cobalt and
nickel isotopes produced by a chemically selective
laser ion source : towards 58Ni (KULeuven)
Investigation of the heavy hydrogen isotope 5H by the
7
Li(6He,8Be)5H reaction (UCL – Univ. Edinburgh –
LPC Caen – FLNR Dubna)
The 15O + α reaction (UCL)
Laser Ion Source (KULeuven)
Hours
85
%
6.2
108
7.9
50
3.7
166
12.3
153
11.3
104
7.7
32
2.4
140
10.3
168
12.4
153
196
1355
11.3
14.5
100.0
Table 7a : Beam time allocation to physics experiments in 2003 using CYCLONE110.
113
PH-188
PH-201
PH-206
Tests of the ARES Spectrometer with (α,γ)
reactions (UCL)
Measurement of the 19Ne(p,γ)20Na reaction in
ARES (UCL)
The 15O + α reaction (UCL)
Hours
192
%
37.6
208
40.7
111
511
21.7
100.0
Table 7 b: Beam time allocation to physics experiments in 2003 using CYCLONE44.
The allocation of beam time to Applications is given in table 8.
Hours
173
%
11.5
238
15.8
Study of the modification of polymers by irradiation,
creation of nanostructures
26
1.7
Study of radiation effects (protons, neutrons) on
components used by the LHC accelerator and CMS,
ATLAS, … experiments
Study of radiation effects (protons, neutrons, heavy
ions) on components used in space
Study of surface properties and wear of ceramic
materials and polymers with implanted 7Be
482
32.1
528
35.1
57
3.8
1504
100.0
Radiobiology – Dosimetry
Production of microporous membranes
Table 8 : Beam time allocation to Applications in 2003.
3. RESEARCH AND DEVELOPMENT
3.1. Development and Production of Radioactive Ion Beams (RIB)
3.1.1. Operation with RIB
This year a record 1207 hours of radioactive ion beams have been produced, mainly for physics but also
for applications. For the first time, experiments were performed with 7 different RIBs in one year. Both
Cyclone110 and Cyclone44 have been used as post-accelerator. The robustness of the standard LiFC targets has
again been demonstrated, as almost 1000 hours (all 6He, 15O, 18Ne and 19Ne beams) were produced with only 2
different units. This amounts to an average integrated dose of more than 1.5 1021 protons per target.
The accurate and reproducible production of these radioactive beams requires an important amount of
work, as well for the start-up and preliminary testing of all sub-systems as for the preparation of the beams. We
mention hereafter a few crucial points.
At the production stage, we must :
-
fabricate and implement several special targets, able to disperse kW’s of beam power during days or even
weeks, with a great release efficiency of the produced isotope and a minimum of outgassing ;
-
produce continuous and stable proton beams of 200 to 300 µA with CYCLONE30.
At the ionisation stage, we must optimise all the parameters of the ECR source (magnetic field profile,
micro-wave power, operational pressure and extraction optics) to assure a maximal ionisation efficiency.
At the acceleration/purification stage, we must find CYCLONE 110 or CYCLONE44 adjustments,
which give, at the same time, a sufficient rejection of stable isobars (a rejection factor which can reach 1 million
for a relative mass difference of 10-4) and a maximal acceleration efficiency.
114
3.1.2. First experiment using a 10C beam
The 10C beam developed last year was successfully used for experiments this year. The 10C2+ beam
averaged about 104 pps over the 6-day run. The challenges for optimizing the beam, monitoring the intensity
during the experiment and ensuring good isobaric purification with such low currents was solved by using a
secondary electron emitting foil in combination with the in-house developed high gain (up to a factor of 106)
current amplifiers.
3.1.3. First experiment using an 15O beam
Also the 15O beam, under development for a few years, has been used for experiments for the first time
this year. Unfortunately, vacuum problems caused somewhat less than ideal conditions in the course of the
experiment. Still, an average intensity of 107 pps was obtained over the run.
3.1.4. Increased 18F average intensity using a dual trap
Another experiment using the semi-on-line produced 18F beam was run this year. Further
improvements on the production system were performed. An additional trap, which stores the 18F coming from
the off-line chemistry before injection into the ECR source, was added. In this way, production batches could be
prepared in one trap while the beam was being provided with the other trap. Switching time between traps was
improved which increased the duty cycle in batch processing, essentially resulting in more hours of beam-ontarget per shift. Also the intensity of 18F per batch was increased to over 1 Ci per batch, with batches arriving at
the source approximately every 3 hours.
The available Radioactive Ion Beams are given in table 9.
T1/2
q
6
0.8 s
7
53 days
1+
2+
1+
2+
1+
2+
1+
1+
2+
3+
2+
Element
Helium
Beryllium
10
19.3 s
11
20 min
10 min
Carbon
Carbon
Nitrogen
13
15
2 min
18
110 min
1.7 s
Oxygen
Fluorine
Neon
18
19
17 s
35
1.8 s
Neon
Argon
•
†
2+
2+
3+
2+
2+
3+
4+
3+
5+
Intensity
[pps]*
9·106
3·105
2·107
4·106
2·105
1.104
1.107
4·108
3·108
1·108
6·107
1.108
5·106
6·106
4·106
2·109
5·109
1.5·109
8·108
2·106
1·105
Energy range
[MeV]
5.3-18
30-73
5.3-12.9
25-62
5.6-11
24-44
6.2-10
7.3-8.5
11-34
45-70
10-29
6-10.5 †
11-24
11-24
24-33,45-55
11-23
4 -9.5†
23-35,45-50
60-93
20-28
50-79
Typical intensity at the experiment location (after acceleration and separation)
With CYCLONE44
Table 9 : List of Available Radioactive Ion Beams at Louvain-la-Neuve.
3.2. Additional tests for 39Ar measurements
Additional measurements were performed with the SCAMPI ECR source in the context of a possible
AMS measurement of 39Ar (see Progress Report 2002). The maximum Ar8+ current that can be extracted from
the ECR source SCAMPI in its current configuration was determined at 120 µA at 10 kV. However, by using a
115
fixed 36Ar gas flow and increasing the 40Ar flow, it was observed that the acceleration efficiency drops
significantly with increased flow rate. This is due to space charge effects and to a poor extraction geometry. To
be able to accelerate as high currents as possible, this extraction region will have to be improved.
Further tests on the reduction of 39K from the source have been performed. One measurement used the
heated quartz liner developed for the 7Be beam. The idea was to bake-out the potassium from the source. A
large increase in the amount of extracted potassium was observed and a strong reduction of the argon current
have been observed. This geometry proved thus to be uninteresting for this application.
A repetition of the run of 2002 with silane conditioning has shown the reproducibility of the method.
Again a potassium reduction of about 98-99% was obtained. Furthermore, the use of an enriched 83Kr leak
almost completely eliminated the background of 78Kr (same m/q ratio). However, the initial potassium
contamination was much larger. Cleaning techniques for the plasma chamber will have to be investigated in
detail.
3.3. CYCLONE44
3.3.1. First full experiment with RIBs at CYCLONE44 (19Ne)
After many hours of experiments with stable beams and some tests with post-accelerated radioactive
beams, the first long experiment with RIBs at Cyclone 44 was performed this year. Two week-long runs with
19
Ne3+ beams were performed using this youngest member of the CYCLONE family in conjunction with the
ARES recoil separator. The experiment was performed at a low post-accelerated energy of 0.5 MeV/amu.
3.3.2. Control system development
While maintaining permanently a viable control system of CYCLONE44, necessary for beam
developments and physics experiments, we have continued the developments initiated last year, namely the
transfer from COROS to WINCC and the integration of the still manually controlled parts.
The existing S5 PLC programme has been entirely rewritten and simplified to obtain a complete
separation between the control/safety functions and the operator interface. The operator interface function is now
transferred to the WinCC level.
Simplified but realistic representations of the different machine parts and beam lines have been adopted
for the HMI (Human-Machine Interface). This philosophy allows to represent a maximum of Process
information, useful for diagnostic in case of failure, while favouring a simple and intuitive interface to avoid
hesitation and operational mistakes. Navigation between pages is possible either from the external branching
system generated by WinCC or from buttons located in the different views. The different commands and
adjustments are directly accessed from windows which appear by clicking on the elements shown. Synoptic
views have been created in parallel to allow experienced operators and users to access a large number of
parameters in a swift and direct way. Figures 1 to 3 show screens corresponding respectively to the cyclotron, to
the low energy beam injection line and to a synoptic view gathering the powersupply adjustments of the low
energy beam injection line.
116
Figure 1 : CYCLONE44 – General View.
Figure 2 : Low Energy Beam Injection Line – General view.
117
Figure 3 : Low Energy Beam Injection Line – Synoptic 1.
To date the system contains already 1100 input/outputs covering partially all subsystems required for
RIB tuning: the on-line RIB-ECR source, the low energy beam transport and injection lines, CYCLONE44, and
the medium energy transport line up to the ARES target. Cabling and programming are still in progress to
transfer the controls of the vacuum system, to integrate the controls of the local ECR source in the system and to
add other practicalities (e.g. encoders, …).
3.3.3. Other developments
The following beams have been developed : 19Ne3+ at 10.2 MeV, 21Na3+ at 8.61 MeV and 23Na3+at 9.43
MeV for the PH-201 experiment ; 14N2+ at 6.5 and 10 MeV, analog beams for the planned 14O beams (T1/2 = 70s).
The exit line has been further equipped and adapted to be compatible with the new control system:
vacuum pumps and isolation valves have been added and several remotely controlled Faraday cups have been
installed to allow beam intensity measurements in the femto- to micro-ampere range. The slit positioning
systems have been improved.
A retractable beam intensity attenuator (attenuation factor of about 100) and a β+ RIB identifying
system have been installed on the low energy beam line, respectively inside and outside the CYCLONE110
vault.
The RF system start-up has been modified to avoid multipactoring, and new ADC’s with higher
precision have been installed.
3.4. ECR Ion Source Development
3.4.1. New 23Na beam for CYCLONE44
At the request of the 19Ne experiment at CYCLONE44 (PH-201) a 23Na beam had to be developed in a
very short time. Because no oven was available at the ECR source and no sputtering experience with Na was
available in the lab, we tried the method of a heated plasma chamber. This technique was initially developed for
the production of 7Be beams, but later evolved into a more elaborate actively heated chamber. In the initial
118
version, used here for the sodium beam, it consists of a thermally insulated tantalum liner inserted into the
existing copper chamber. The plasma heats the liner up to above 400° C. By inserting tiny amounts of sodium
in the source on the liner, a reasonable partial pressure of Na could be obtained. This vapor was then ionized and
extracted from the source. About 100 nA of 23Na3+ were obtained in this way with only a few tens of watts of
microwave power. The whole system was put in place, tested and operated in one week’s time only.
3.4.2. New ion cocktail with SCAMPI
With the SCAMPI source, we have developed a new “cocktail” of heavy ion beams of ratio near 3.3
(13C4+, 22Ne6+, 28Si8+, 40Ar12+, 58Ni17+, 83Kr25+) having penetration depths of at least 100 µm. In the frame of our
collaboration with ESA, they will allow the study of the behaviour under radiation of the new generation
integrated circuitry.
3.5 Technological Applications
3.5.1. Two successful runs of 7Be for applications
Two runs with 7Be were performed for wear application measurements. Production samples for the
automotive industry (engine parts of Formula 1 racing cars) as well as samples for research (polymers) were
implanted with 7Be atoms. The implantation depth was typically 2 µm (homogeneous) or 1µm (peak) and the
number of implanted atoms was around 1011 atoms. The automated tilted foil energy degrader was again used
for the homogenous implantation. The beam intensity during implantation was typically 3 to 5 107 pps.
3.5.2. Heavy ion Irradiation Facility
During 2003, 660 hours in heavy ions have been scheduled for electronic device testing and
characterization.
The following table presents the different experiments, classified by user, using the "Heavy Ion
Irradiation Facility" (HIF).
Institute / Company
UCL/FSA/ELEC/DICE
UCL/CRC + ESA
Alcatel ETCA, Belgium
ESA, Netherlands
SAAB, Sweden
TIMA, France
HIREX, France
Astrium, United Kingdom
Astrium, Germany
IMEC, Belgium
TRAD, France
Astrium, France
ONERA, France
SOREQ, Israel
Alcatel, France
ATMEL, France
Purpose
SEE in EEPROM and FRAM.
Beam technical developments ans qualification.
New technology tests.
SEE in volatge regulators.
FPGA testing.
FPGA testing.
SEB – SEGR in Power MOS.
SEE in SDRAM and FRAM.
High Frequency RX/TX modules.
LU tests on operational amplifiers
SEL + SET on imager.
SEE characterization of SRAM.
SEE in transceivers.
Transistor testing.
SEB / SEGR on power transistors.
Laser / HI SEE data correlations on photodiodes and operational amplifiers.
SEE in SDRAM.
SET + LU on DAC
LU on linear devices
LU in FIFO.
LU in SRAM and FPGA.
SEE on oven controlled cristal oscillator.
ASIC characterization.
FPGA testing.
119
Several periods have been dedicated to beam technical developments:
• Production of 10 B 2+ using MIVOC technique.
• Production and acceleration of 83 Kr 21+ at 574 MeV and 86 Kr 22+ at 608 MeV.
• Development of a new ion cocktail M/Q = 3.33
The idea of the latest development is to take new device technologies into account. Many new devices present
central bonding and lead frames. Nowadays, thinned dies need to be backside irradiated. For this, a 40 µm
penetration depth beam is not sufficient. The new cocktail tends to address this by increasing the ion charge
state. In this way, larger energies are available and ranges of 100 µm are now available. The table hereafter
presents the full specifications for this new beam :
Ion
C - 13
Ne - 22
Si - 28
Ar - 40
Ni - 58
Kr - 83
Range(Si)
LET(Si)
LET(Si)
cyclo
cyclo
E DUT
DUT
Ecyclo
[µm]
[MeV] [MeV/mg /cm²]
[MeV] [MeV/mg /cm²]
133
1,2
276
131
1,2
177
4
129
170
4,1
248
6,6
115
236
6,8
390
9,9
125
372
10,1
538
21,2
92
500
21,9
813
31
100
756
32,4
Charge
4
6
8
12
17
25
Range(Si)
DUT
[µm]
266
122
106
119
85
92
A first test campaign in collaboration with ESA was carried out using this cocktail. A MHS 32 K 8 SRAM tested
using M/Q = 5 beam was cross checked. The presented SEU results show good agreement between the two test
campaigns :
MHS CP65656EV 32K8 SRAM - Heavy Ion SEU
Results (UCL9811 & UCL0311).
1,0E-06
Cross Section - (cm
2
/bit)
1,0E-05
1,0E-07
1,0E-08
3
1,0E-09
4
5
6 7
13
12
11
10
8
UCL9811 - M31
2
1,0E-10
UCL9811 - M32
UCL0311 - M31
1
UCL0311 - M32
1,0E-11
0
10
20
30
40
50
2
Ion LET - MeV/(mg/cm )
Point
1
2
3
4
5
6
7
8
9
10
11
12
13
Ion
C 13
Ne 22
Ne 22
Ne 22
Ar 40
Ar 40
Ar 40
Ni 58
Ni 58
Ni 58
Kr 83
Kr 83
Kr 83
Angle [°]
60
0
45
60
0
45
60
0
45
60
0
45
60
120
60
70
3.5.3. Neutron Irradiation Facility (NIF)
During 2003, 72 hours in monoenergetic neutrons (in cave Q) have been scheduled for electronic
device testing and characterization.
Hirex company (France) used 65 MeV, 45 MeV and 25 MeV primary proton beams to characterize
SRAM. Later correlation with neutron white spectra (Los Alamos) will be carried out to verify the JEDEC
standard.
3.5.4. Proton Irradiation Facility (LIF)
During 2003, 168 hours in protons have been scheduled for electronic device testing and
characterization.
The following table presents the different experiments, classified by user, using the "Light Ion
Irradiation Facility" (LIF).
Institute / Company
INFN Padova/CMS barrel
muon drift tubes
CERN
INFN Pavia/ ATLAS MDT
– TGC chambers
CAEN
INFN Roma/ATLAS barrel
level 1 muon trigger – RPC
system
Nikhef/ATLAS
IMEC
HIREX
Components
Bipolar COTS, CMOS COTS, ASIC CMOS and BiCMOS COTS
TMS320C30 DSP
HC16 microcontroller
SRAM and FRAM
Vacuum gage and controllers
Communication controller
LV regulators
Monitoring circuitry
8 HV DC-DC channels
8 HV linear channels
HV board
Phase detector
CMOS/ECL translator
Coincidence matrix ASIC
Fairchild driver and receiver
ELMB 128
CCD sensors
SRAM
3.6 MISCELLANEOUS
The fire safety of the experimental hall has been considerably improved : wooden constructions have
been treated with a fire retarding paint or have been replaced by metallic constructions. The borated paraffin
shielding around parts of the beam lines has been replaced by a mixture of borax and polyethylene chips, packed
in metallic cans.
The shielding between the DEMON/W1,W2 switchyard and the HIF/DEMON area has been reinforced.
Following a powerful lightning strike on the building, considerable irradiation doses have been
registered on all dosimeters present in the building. To exclude all other possible causes, an extensive study has
been made to correlate the absorbed doses on more than one hundred dosimeters to their location at the moment
of the lightning strike.
121
V. LOGISTIQUE
1. MECANIQUE
W. Binon, R. Bouchonville, Th. Debuck, J.-M. Delforge, C. Felix, P. Nemegeer
Les principaux ensembles de pièces réalisés à l’atelier de mécanique au cours de l’année 2003 sont
repris ci-après.
Pour l’expérience CMS :
-
nombreux prototypes de gabarit pour le cintrage de tuyaux en titane servant au refroidissement des pétales du
tracker ;
gabarits de positionnement et de collage des échangeurs thermiques des pétales ;
huit groupes-générateurs 500 Watts de liquide froid C8H18 pour le refroidissement des pétales, à la demande
du CERN et des laboratoires associés ;
une installation complète de soudure laser avec commande numérique pour circuits de refroidissement des
pétales.
une presse pneumatique de 800 kg à grands plateaux pour collage de peaux en fibre de carbone ;
une porte de boîte froide avec traversées multiconducteurs étanches pour essais de pétales complets ;
un chassis d’alimentation refroidi pour essais électroniques des modules ;
des prototypes de connecteurs en titane pour liquide froid ;
une boîte froide de grandes dimensions pour essais de pétales sous atmosphère et température
programmables.
Dans le cadre de la campagne de vols paraboliques 2003 sous l’égide de l’Agence Spatiale
Européenne :
-
construction d’un dispositif embarqué pour interférométrie optique avec suspension cardan.
Pour les expériences de physique et d’astrophysique nucléaire et pour les cyclotrons :
-
des supports pour diverses cibles utilisées lors des expériences ;
des fentes de divergence pour ARES ;
des atténuateurs de faisceau pour la « rue neuve » ;
des pièces pour l’insertion d’un détecteur β+ sur la « rue neuve » ;
les modifications de la voie de sortie de CYCLONE44
des cibles de LiF/C et des ensembles porte-cibles pour la production de faisceaux radioactifs ;
des supports de condensateur pour les amplis HF de CYCLONE110 ;
des pièces pour la source CUSP H- et pour la télécommande des aimants 15° de CYCLONE30 ;
des cages de Faraday de précision pour les mesures de très faibles intensités de faisceau ;
une nouvelle passerelle en acier donnant accès aux locaux autour du séparateur LISOL.
Pour les sources ECR :
-
des nouvelles brides d’injection ;
des pièces de mesure de champ, de sputtering et de support pour le four ;
des pièces pour l’injection de carbonate de bore (C2 B10 H12) pour des essais de production de B2+ par la
méthode MIVOC (production du gaz à partir d’une poudre).
Pour les applications :
-
des supports et un chariot pour la cage de Faraday mobile pour la voie d’irradiation par protons ;
les pièces pour le dispositif de balayage en énergie (bras pivotant) pour l’implantation de 7Be et pour le
positionnement des échantillons.
Pour des entités extérieures :
-
des pièces pour le positionnement du malade pour l’unité MD/RIM/RBNT ;
un détecteur de rupture pour l’unité FSA/AUCE/GCE.
un module de perfluoration avec marquage au 18F pour l’unité MD/MINT/TOPO ;
122
-
un système de convoyeur de cibles pour NORDION.
2. BUREAU DE DESSIN
B. Florins, E. Lannoye
Les principaux projets qui ont été étudiés et dessinés sont repris ci-après :
-
les modifications de la voie de sortie de CYCLONE44 ;
les fentes de divergence pour les voies de faisceau de CYCLONE44 ;
l’équipement de la « rue neuve » avec des atténuateurs d’intensité de faisceau et avec un détecteur β+ ;
les diverses adaptations de la source ECR (SCAMPI) ;
un système de positionnement de la sonde à effet Hall pour la mesure du champ magnétique des
quadrupôles ;
le système de bras pivotant et la fixation des échantillons pour l’implantation de 7Be ;
une nouvelle passerelle d’accès aux locaux autour de LISOL ;
des « clean cells » pour les essais des détecteurs Si du « tracker » de CMS.
Les plans d’ensemble du hall des cibles et du transport de faisceau de CYCLONE44 ainsi que la coupe
au plan médian de CYCLONE44 ont été mis à jour. Des rendus réalistes du hall des cibles et de l’implantation
de CYCLONE44 ont été créés. Un plan volumique de la tour E et un plan complet du batiment Marc de
Hemptinne ont été créés. Divers posters pour des conférences et des expositions ont été conçus.
3. ELECTRONIQUE
3.1. Atelier d’électronique : activités pour CMS
3.1.1. FHIT
Cet appareil est destiné à tester les « Front End Hybrids » (FEH) de CMS.
Le FEH a pour fonction d’amplifier et transmettre les données provenant des senseurs multipistes au
silicium.
CMS en contient plus de 10000 au total, répartis en 15 variantes selon leur emplacement dans le
détecteur.
Cette année, le projet a été poursuivi :
-
construction de 10 FHIT en version simple ou double
conception et fabrication de systèmes de positionnement pour pointe de test
révision des adaptateurs pour les différentes variantes et fabrication de 100 pièces
développement d’une version « light » : le LFHIT dont cinq exemplaires ont été livrés et vingt sont en
fabrication.
développement et fabrication d’outillage pour la manipulation des FEH (50 pièces fabriquées)
révisions du Firmware (programme) en fonction des nouvelles variantes, des changements de spécifications,
des données à stocker dans la database, etc..
développement de fonctions supplémentaires pour le dépannage des FEH défectueux
3.1.2. Petal assembly and Burn-in
NIM-LVDS
Ce module a été développé en collaboration avec le groupe CMS de l’Universiteit Antwerpen et
fabriqué en 15 exemplaires. Il intervient dans la distribution des signaux de test vers les modules constituant un
pétale.
123
INTERLOCK board
Ce module fait partie de l’installation de « burn-in » (test d’endurance). Il est chargé de mettre fin au
test en cas de défaillance d’un des contrôleurs du processus (Slow control).
Ce module est en développement.
VUTRI
Nous avons fabriqué quatre modules VUTRI (développés au CERN).
3.1.3. L’atelier d’électronique est impliqué quotidiennement dans les diverses activités
du groupe CMS
-
support et refroidissement des pétales
test des senseurs, maintenance de la « probe station »
presse pour le collage des supports de pétales (contrôle pneumatique)
installation de chambre grise
climatisation, etc..
3.2. Autres activités
-
fabrication de 10 compteurs à 16 voies
support pour l’expérience en apesanteur APTOVOL
4. LOGISTIQUE INFORMATIQUE
Fabian Boldrin, Thomas Keutgen et Alain Ninane (responsable)
4.1. Gestion du parc informatique
Outre la gestion quotidienne de notre parc informatique, installation de systèmes, gestion des
utilisateurs, ..., l’équipe informatique s’est concentrée sur les points suivants :
•
la migration des stations de travail de Windows NT vers Windows 2000 dans l’environnement FYNU2K est terminée;
•
•
•
•
la migration des stations de travail Linux de RedHat 7.2 vers RedHat 7.3 est terminée;
des procédures automatiques de gestion et de monitoring des systèmes Linux ont été mises en place;
les anciens serveurs Digital Alpha fynusrv2 et fynusrv5 sont démantelés;
le serveur Linux Digital fynusrv4 est démantelé; le service de validation de login UNIX (Network
Information Service – YP/NIS) a été transféré vers le serveur DELL Linux server01;
le serveur Windows NT Digital fynusrv1 est démantelé;
les stations de travail Digital UNIX du bureau de CAO ont été démantelées tandis que l’application de
CAO, Euclid, était migrée sur des nouvelles stations de travail Compaq sous Windows 2000.
la salle des serveurs située au fond de la salle de commande est maintenant désaffectée, les machines
encore en fonctionnement ont été déplacées vers le local E.083 et la baraque PAI suivant leur rôle;
des points d’accès en réseau sans-fil ont été installés au deuxième et troisième étage de la tour de
physique nucléaire.
•
•
•
•
Par ailleurs, le site Web de notre Institut a été redessiné. Une attention toute particulière a été apportée à
la documentation de notre réseau informatique.
124
L’ensemble des PCs sous Linux ainsi que le cluster de calcul ont été intégrés dans l’environnement
Condor2, un système de gestion de calcul à haute performance distribué. Notre environnement Condor est à ce
jour constitué de 63 CPUs et le temps de calcul utilisé en 2003 est de l’ordre de 120.000 heures.
4.2. Développements pour CMS
Une nouvelle campagne de mesures des performances de protocoles réseaux a été entreprise dans le
cadre du démonstrateur de l’Event Builder CMS. Ce démonstrateur est constitué d’un ensemble de 64 PCs
équipés de processeurs Intel Pentium III à 733 et 1000 MHz. Les PCs sont connectés via des cartes Ethernet
Gigabit Alteon à un switch Gigabit à 64 portes de la société Foundry. La figure 1 compare les performances des
protocoles TCP/IP, Layer 2 socket et Layer 2 zero-copy. Les figures 2 et 3 montrent la scalabilité des
performances des protocoles TCP/IP et Layer 2 socket en fonction du nombre de systèmes utilisés dans le
démonstrateur.
Figure 1 : Streaming throughput versus packet size.
2
http://www.cs.wisc.edu/condor/
125
Figure 2 : Throughput versus demonstrator size – TCP/IP.
Figure 3 : Throughput versus demonstrator size – Layer 2 socket.
A l’heure actuelle, les performances de TCP/IP sont telles que ce protocole ne sera pas utilisable dans
l’Event Builder CMS. Des tests sur de nouvelles cartes Intel E1000 et de nouvelles versions du kernel Linux sont
en cours pour le moment.
126
VI. ANNEXES
1. Publications dans des revues
C. Angulo, G. Tabacaru, M. Couder, M. Gaelens, P. Leleux, A. Ninane, F. Vanderbist, T. Davinson, P.J. Woods,
J.S. Schweitzer, N.L. Achouri, J.C. Angelique, E. Berthoumieux, F. de Oliveira Santos, P. Himpe, P.
Descouvemont, Identification of a new low-lying state in the proton drip line nucleus 19Na, Phys. Rev.
C67 (2003) 014308 (4 pages).
C. Angulo, M. Azzouz, P. Descouvemont, G. Tabacaru, M. Cogneau., M. Couder, M. Gaelens, P. Leleux, M
Loiselet, G Ryckewaert, F. Vanderbist, T. Davinson, D. Baye, A. Di Pietro, P. Figuera, R.G. Pizzone, F.
de Oliveira Santos, N. de Séréville, Experimental determination of the 7Be+p scattering lengths, Nuclear
Physics A716 (2003) 211-219.
C. Angulo, P. Descouvemont, M. Couder, M. Gaelens, P. Leleux, A. Ninane, G. Tabacaru, F. Vanderbist, T.
Davinson, Ph.J. Woods, J.S. Schweitzer, N.L.Achouri, J.C. Ange1ique, E. Berthoumieux, F. de Oliveira
Santos, P. Himpe, Spectroscopy of the proton drip line nucleus 19Na by 1H(18Ne,p)18Ne elastic
scattering, Nuclear Physics A719 (2003) 201c- 204c.
C. Angulo, P. Descouvemont, M. Cogneau., M. Couder, M. Gaelens, P. Leleux, M Loiselet, G Ryckewaert, G.
Tabacaru, F. Vanderbist, T. Davinson, M. Azzouz, D. Baye, A. Di Pietro, P. Figuera, R.G. Pizzone, F.
de Oliveira Santos, N. de Séréville, The elastic scattering 7Be+p at low energies: implications on the
7
Be(p,γ)8B S-factor, Nuclear Physics A719 (2003) 300c-303c.
C. Angulo, Spectroscopy of the proton drip line nucleus 19Na by 1H(18Ne,p)18Ne elastic scattering, Proceedings
of the Second International Symposium on Proton-Emitting Nuclei, PROCON 2003, Legnaro, Italy, 1215 February, 2003 (Eds. E. Maglione and F. Soramel), AIP Conference Proceedings n. 681, p217-226,
ISBN 0-7354-0159-0.
S. Assouak, E. Forton, Gh. Grégoire, Irradiations of CMS Silicon sensors with fast neutrons, Nuclear
Instruments and Methods in Physics Research A514 (2003) 156-162.
M. Bernas, P. Armbruster, J. Benlliure, A. Boudard, E. Casarejos, S. Czajkowski, T. Enqvist, R. Legrain, S.
Leray, B. Mustapha, P. Napolitani, J. Pereira, F. Rejmund, M. V. Ricciardi, K.-H. Schmidt, C. Stéphan,
J. Taieb, L. Tassan-Got, C. Volant, Fission residues produced in the spallation reaction 238U + p at 1 A
GeV, Nucl. Phys. A 725 (2003) 213-253.
J. Cabrera, Th. Keutgen, J. Cabrera, Th. Keutgen, Y. El Masri, Ch. Dufauquez, V. Roberfroid, I. Tilquin, J. Van
Mol, R. Régimbart, R.J. Charity, J.B. Natowitz, K. Hagel, R. Wada and D.J. Hinde, Fusion-fission and
fusion-evaporation processes in the 20Ne + 159Tb and 20Ne + 169Tm interactions between E/A = 8 and 16
MeV, Phys. Rev. C68, 034613 (2003) 1-21.
E. Casarejos, P. Armbruster, L. Audouin, J. Benlliure, M. Bernas, A. Boudard, R. Legrain, S. Leray, B.
Mustapha, S. Czajkowski, T. Enqvist, B. Fernandez, J. Pereira, M. Pravikoff, F. Rejmund, K.-H.
Schmidt, C. Stéphan, J. Taieb, L. Tassan-Got, C. Villagrasa, C. Volant, W. Wlazlo, Isotopic production
cross sections of residues in reactions induced by relativistic heavy ions with protons and deuterons,
Phys. At. Nuclei 66 (2003) 1413-1420.
M. Couder, C. Angulo, W. Galster, J.-S. Graulich, P. Leleux, P. Lipnik, G. Tabacaru, F. Vanderbist,
Performance of the ARES recoil separator for (p,γ) reaction measurements, Nuclear Instruments and
Methods in Physics Research A506 (2003) 26–34.
S. Cuenot, C. Fretigny, S. Demoustier-Champagne, B. Nysten, Measurement of elastic modulus of nanotubes by
resonant contact atomic force microscopy, Journal of Applied Physics 93 (9) (2003) 5650.
127
M. Cyamukungu, Gh. Grégoire, P. Stauning, J. Lemaire, The Charged Particle Detector : Characteristics and
Flux Calculation Code, Technical Note ESA/ESTEC contract No: 16709/02/NL/EC, Louvain-laNeuve, 14 June 2003 (Rapport d’Expertise).
F. Dehaye, E. Balanzat, E. Ferain, R. Legras, Chemical modifications induced in bisphenol-A polycarbonate by
swift heavy ions, Nuclear Instruments and Methods in Physics Research B209 (2003) 103.
Th. Delbar, D.Favart, Gh. Grégoire, S. Kalinin, I. Maklioueva and the CHORUS collaboration, Measurement of
Λ c+ production in neutrino charged-current interactions, Phys. Lett. B555 (2003) 156-166.
Th. Delbar, D.Favart, Gh. Grégoire, S. Kalinin, I. Maklioueva and the CHORUS collaboration, Cross-section
measurement for quasi-elastic production of charmed baryons in νN interactions, Phys. Lett. B575
(2003) 198-207.
Th. Delbar, D.Favart, Gh. Grégoire, S. Kalinin, I. Maklioueva and the CHORUS collaboration, measurement of
the Z/A dependence of neutrino charged-current total cross-sections, Eur. Phys. J. C30 (2003) 159-167.
M. Delvaux, S. Demoustier-Champagne, Immobilisation of glucose oxidase within metallic nanotubes arrays for
application to enzyme biosensors Biosensors & Bioelectronics 18 (7) (2003) 943.
N. de Séréville, A. Coc, C. Angulo, M. Assunçao, D. Beaumel, B. Bouzid, S. Cherubini, M. Couder, P. Demaret,
F. de Oliveira Santos, P. Figuera, S. Fortier, M. Gaelens, F. Hammache, J. Kiener, D. Labar, A.
Lefebvre, P. Leleux, M. Loiselet, A. Ninane, S. Ouichaoui, G. Ryckewaert, N. Smirnova, V. Tatischeff,
J.-P. Thibaud, 2H(18F,p)15N reaction applied to nova gamma-ray emission, Physical Review C67 (2003)
052801(R) (4 pages).
N. de Séréville, A. Coc, C. Angulo, M. Assunçao, D. Beaumel, B. Bouzid, S. Cherubini, M. Couder, P. Demaret,
F. de Oliveira Santos, P. Figuera, S. Fortier, M. Gaelens, F. Hammache, J. Kiener, D. Labar, A.
Lefebvre, P. Leleux, M. Loiselet, A. Ninane, S. Ouichaoui, G. Ryckewaert, N. Smirnova, V. Tatischeff,
J.-P. Thibaud, Study of the 18F(p,α)15O reaction for application to nova γ-ray emission, Nuclear Physics
A718 (2003) 259c-262c.
A. Di Pietro, P. Figuera, F. Amorini, C. Angulo, G. Cardella, S. Cherubini, T. Davinson, D. Leanza, J. Lu, H.
Mahmud, M. Milin, A. Musumarra, A. Ninane, M. Papa, M. G. Pellegriti, R. Raabe, F. Rizzo, C. Ruiz,
A. C. Shotter, N. Soic and S. Tudisco, Light-particle emission in the reaction 6He+64Zn around the
Coulomb barrier, Europhys. Lett. 64 (3) (2003) 309-315.
F. Elhoussine, S. Metefi-Tempfli, A. Encinas and L. Piraux, Quantum conductance in electrodeposited Ni
nanocontacts and magneto-resistance measurements, J. Appl. Phys 93 (2003) 8567.
E. Ferain, R. Legras,Track-etch templates designed for micro- and nanofabrication, Nuclear Instruments and
Methods in Physics Research B208 (2003) 115.
B. Fischer, D. Coelho, P. Dufour, J.-P. Bergerat, J.-M. Denis, J. Gueulette, P.Bischoff, Caspase-8-mediated BID
cleavage in p53-dependent apoptosis, Biochem Biophys Res Co 306 (2003) 516-522.
M. Gaelens, M. Cogneau, M. Loiselet, G. Ryckewaert, Post-acceleration of 7Be at the Louvain-la-Neuve
radioactive beam facility, Nucl. Instrum. and Meth. B204 (2003) 48-52
F. Guisset, S. Ovyn, G, Pfyffer, V. René de Cotret, D. Bertrand, J. Govaerts, Gh. Grégoire, It’s relatively
parabolic: APTOVOL – A Parabolic Test Of the constancy of the Velocity Of Light, EDUnews 5
(2003) 4-5.
P. Kammel, L. Bonnet, J. Deutsch, J. Govaerts, D. Michotte, R. Prieels, and the MuCap and MuLan
Collaborations, Muon Capture and Muon Lifetime, Proceedings of the International Workshop on
Exotic Atoms – Future Perspectives, EXA-2002, Vienna (Austria), November 28-30, 2002, eds. P.
Kienle, J. Marton and J. Zmeskal (Austrian Academy of Sciences Press, Vienna, 2003), 11 pages.
128
V. Lemaitre et ALEPH Collaboration, Measurement of the hadronic photon structure function F2γ (x,Q 2 ) in
two-photon collisions at LEP, Eur. Phys. J. C30 (2003) 145-158.
V. Lemaitre et ALEPH Collaboration, Exclusive production of pion and kaon meson pairs in two photon
collisions at LEP, Nucl. Phys. B569 (2003) 140-150.
V. Lemaitre et ALEPH Collaboration, Search for stable hadronizing squarks and gluinos in e+e- collisions up to
s = 209 GeV, Eur. Phys. J. C31 (2003) 327-342.
V. Lemaitre et ALEPH Collaboration, A measurement of the gluon splitting rate into cc pairs in hadronic Z
decays, Phys. Lett. B561 (2003) 213-224.
V. Lemaitre et ALEPH Collaboration, Measurement of the inclusive D*± production in γγ collisions at LEP,
Eur. Phys. J. C28 (2003) 437-449.
V. Lemaitre et ALEPH Collaboration, Search for supersymmetric particles with R parity violating decay in e+ecollision at s up to 209-GeV, Eur. Phys. J. C31 (2003) 1-16.
V. Lemaitre et ALEPH Collaboration, Search for anomalous weak dipole moments of the tau lepton, Eur. Phys.J.
C30 (2003) 291-304.
V. Lemaitre et ALEPH Collaboration,Single- and multiphoton produciton in e+e- collisions at
Eur. Phys. J. C28 (2003) 1-13.
s up to 209 GeV,
K. Piotrzkowski et ZEUS Collaboration, Measurement of the open-charm contribution to the diffractive proton
structure function, Nuclear Physics B672 (2003) 3-35.
K. Piotrzkowski et ZEUS Collaboration, Measurement of high-Q2 charged current cross sections in e+p deep
inelastic scattering at HERA, European Phys. Journal C32 (2003) 1-16.
K. Piotrzkowski et la Collaboration ZEUS, “Jet production in charged current deep inelastic e+ p scattering at
HERA”, Eur. Phys. J. C31 (2003) 149- 164.
K. Piotrzkowski et ZEUS Collaboration, Measurement of deeply virtual Compton scattering at HERA, Physics
Letters B573 (2003) 46-62.
K. Piotrzkowski et ZEUS Collaboration, Search for resonance decays to lepton+jet at DESY HERA and limits
on leptoquarks, Physical Review D68 (2003) 052004.
K. Piotrzkowski et ZEUS Collaboration, Dijet angular distributions in photoproduction of charm at HERA,
Physics Letters B565 (2003) 87-101.
K. Piotrzkowski et ZEUS Collaboration, Search for single-top production in ep collisions at HERA, Physics
Letters B559 (2003) 153-170.
K. Piotrzkowski et ZEUS Collaboration, Measurement of high-Q2 e-p neutral current cross sections at HERA and
the extraction of x F3 (revised), Eur. Phys. J. 28 (2003) 2, 175-201.
K. Piotrzkowski et ZEUS Collaboration, ZEUS next-to-leading-order QCD analysis of data on deep inelastic
scattering, Phys. Review D67 (2003) 012007.
R. Raabe, A. Andreyev, M. Huyse, A. Piechaczek, P. Van Duppen, L. Weissman, A. Wöhr, C. Angulo, S.
Cherubini, A. Musumarra, D. Baye, P. Descouvemont, T. Davinson, A. Di Pietro, A. M. Laird, A.
Ostrowski, A. Shotter, L. I. Galanina, and N. S. Zelenskaya, 2n-transfer contribution in the
4
He(6He,6He)4He cross section at Ec.m. = 11.6 MeV, Phys. Rev. C67, 044602 (2003).
129
E. Raeymackers, S. Benck, I. Slypen, J.P. Meulders, N. Nica, V. Corcalciuc, A. Koning, Light charged particle
production in the interaction of fast neutrons (25-65 MeV) with uranium nuclei, Phys. Rev. C68 (2003)
024604-1 024604-12.
E. Raeymackers, S. Benck, N. Nica, I. Slypen, J.P. Meulders, V. Corcalciuc, A. Koning, Light charged particle
emission in fast neutrons (25-65 MeV) induced reactions on 209Bi, Nucl. Phys. A726 (2003) 210-230.
M. V. Ricciardi, T. Enqvist, J. Pereira, J. Benlliure, M. Bernas, E. Casarejos, V. Henzl, A. Kelic, J. Taieb, K.-H.
Schmidt, Experimental indications for the response of the spectator to the participant blast, Phys. Rev.
Lett. 90 (2003) 212302.
X. Rouby, Testing and characterizing CMS tracker front-end hybrids, Physicalia Magazine, 25-3 (2003) 149158.
A. Saib, D. Vanhoenacker-Janvier, I. Huynen, A. Encinas, L. Piraux, E. Ferain, R. Legras, Magnetic photonic
band-gap material at microwave frequencies based on ferromagnetic nanowires, Appl. Phys. Lett. 83
(12) (2003) 2378.
D.V. Shetty, A. Keksis, E. Martin, A. Ruangma, G.A. Souliotis, M. Veselsky, E.M. Winchester, S.J. Yennello,
K. Hagel, Y.G. Ma, A. Makeev, N. Marie, M. Murray, J.P. Natowitz, L. Qin, P. Smith, R. Wada, J.
Wang, M. Cinausero, E. Fioretto, G. Prete, D. Fabris, M. Lunardon, G. Nebbia, V. Rizzi, G. Viesti, J.
Cibor, Z. Majka, P. Staszel, R. Alfaro, A. Martinez-Davalos, A. Menchaca-Rocha, Y. El Masri, T.
Keutgen, Intermediate mass fragments and isospin dependence in 124Sn, 124Xe + 124Sn, 112Sn reactions at
28 MeV/nucleon, Phys. Rev. C68 (2003) 054605 (1-11)
G. Stenuit, S. Michotte, J. Govaerts, L. Piraux and D. Bertrand, Vortex Configurations in Mesoscopic
Superconducting Nanowires, Proceedings of the International Conference on Modern Problems in
Superconductivity, Yalta (Ukraine), September 9 – 14, 2002, ed. S. Kruchinin, Mod. Phys. Lett. B17
(2003) 537-547.
G. Stenuit, S. Michotte, J. Govaerts and L. Piraux, Vortex Matter in Lead Nanowires, Eur. Phys. J. B33 (2003)
103-107.
J. Taieb, K.-H. Schmidt, L. Tassan-Got, P. Armbruster, J. Benlliure, M. Bernas, A. Boudard, E. Casarejos, S.
Czajkowski, T. Enqvist, R. Legrain, S. Leray, B. Mustapha, M. Pravikoff, F. Rejmund, C: Stephan, C.
Volant, W. Wlazlo, Evaporation residues produced in the spallation reaction 238U + p at 1 A GeV,
Nucl. Phys. A724 (2003) 413-430.
2. Communications et participations à des Congrès
-
BNS evening session - Nuclear Applications in Space, December 12, 2002, Brussels, Belgium
M. Cyamukungu, Detection of charged particles trapped by the earth magnetosphere (Invited lecture).
-
3rd Relativistic Electron Workshop / SAMPEX team meeting, January 6-10, 2003, Maui, Hawaï
M. Cyamukungu, A Model of Oersted/CPD Energetic particles compared to SAMPEX/PET results.
-
CMS tracker-week CERN, January 29, 2003, Genève, Suisse
L. Bonnet, V. Lemaître, X. Rouby, FHIT status.
-
GSI Town Meeting, 30 January-1 February, 2003, Darmstadt, Allemagne
C. Angulo, Radioactive Nuclear Beams: Essential Tools in Nuclear Astrophysics (talk).
-
Second International Symposium on Proton-Emitting Nuclei, PROCON 2003, February 12-15, 2003,
Legnaro, Italy
C. Angulo, Spectroscopy of 19Na by 18Ne+p Elastic Scattering (Invited talk).
-
n_TOF Winter School on Astrophysics, ADS and First Results, February 24-28, 2003, Centre de Physique
des Houches, France
130
C. Angulo, Stellar Reaction Rates: Definitions, Evaluations and Data Libraries (Invited lecture).
-
RERMM study progress meeting, April 9, 2003, Nice, France
M. Cyamukungu, Presentation of the CSR Technical report on Oersted/CPD data.
-
2ème Congrès International “Physique des Interactions Rayonnement-Matière “PIRMII””, février 2003,
Marrakech, Maroc
Y. El Masri, F. Vanderbist, V. Zaconte, Ch. Heitz, J. Cabrera, Ch. Dufauquez, V. Roberfroid, M. Couder, P.
Leleux, Th. Keutgen, G. Tabacaru, C. Angulo et M. Loiselet, Analyse quantitative d’4He implanté dans des
feuilles d’aluminium utilisant la rétrodiffusion proton et la technique ERDA, Contribution CA 117
(Conference Proceedings).
Ch. Dufauquez, J. Cabrera, V. Roberfroid, Th. Keutgen, A. Ninane, C. Angulo et Y. El Masri, Production de
particules neutres et chargées légères dans l’interaction des faisceaux de protons et d’alpha avec une cible de
nat
Si entre 20 et 65 MeV, Contribution conférence session plénière, CO41 (Conférence Proceedings).
-
International Conference on Mathematics, Nuclear Physics and Applications in 21st Century, March 8-13,
2003, Le Caire, Egypte
Participants : Th. Delbar, R. Prieels
- XXXIII Rencontres de Moriond : Workshop on "Radioactive beams for nuclear physics and neutrino
physics", 17-22 mars 2003, Les Arcs, Savoie, France
G. Ryckewaert, Acceleration of RIB using cyclotrons.
-
2nd Irradiation Qualification Control Workshop, 15 mai 2003, Louvain-la-Neuve
E. Forton ,S. Assouak, Gh. Grégoire, Setup ofr sensor irradiation qualification.
S. Assouak, E. Forton, Gh. Grégoire, Measurements report.
-
13th IEEE NPSS Real Time Conference, May 18-23, 2003, Montréal, Canada
L. Berti, V. Brigljevic, G. Bruno, E. Cano, A. Csilling, S. Cittolin, S. Erhan, D. Gigi, F. Glege, R. GomezReino Garrido, M. Gulmini, J. Gutleber, C. Jacobs, M. Kozlovszky, H. Larsen, I. Magrans, G. Maron, F.
Meijers, E Meschi, S. Murray, A. Ninane, A. Oh, L. Orsini, L. Pollet, A. Racz2, D. Samyn,
P. Scharff-Hansen, P. Sphicas, C. Schwick, N. Toniolo, L. Zangrando, The Event Builder of the CMS
Trigger and Data Acquisition System
-
Workshop on “Noble gas nuclei in hydrology”, May 21, 2003, Vienna, Austria
Participant : M. Loiselet
-
Société Belge de Physique, General scientific meeting, May 27-28, 2003, Gand, Belgique
L. Bonnet, V. Lemaître, X. Rouby, Testing and characterizing CMS tracker front-end hybrids.
S. Assouak, E. Forton, Gh. Grégoire, Test of radiation hardness of CMS Tracker silicon microstrip detectors.
Conference on Accelerator Applications in a Nuclear Renaissance, June 1-5, 2003, San Diego, USA
J.P. Meulders et al, Neutron-Induced Light-Charged Particle Production (25 to 65 MeV) on Elements of
ADS-Interest (talk).
-
International Conference on Collective Motion in Nuclei under Extreme Conditions (COMEX1), June 10-13,
2003, Paris, France
J. Cabrera, Th. Keutgen, Y. El Masri, V. Roberfroid, I. Tilquin, Ch. Dufauquez, A. Ninane, R. Régimbart,
R.J. Charity, D. Hinde, J.B. Natowtiz, K. Hagel and R. Wada, Study of fusion-fission and fusion-evaporation
in 20Ne + 159Tb interaction between 8 and 16 MeV/nucleon, Contribution (Conference Proceedings p. 56).
-
6ème Colloque International de Radiobiologie Fondamentale et Appliquée (CIRFA) du 20 juin au 4 juillet
2003, Batz-sur-Mer, France
B. Fischer, D. Coelho, S. Benzina, J.P. Denis, J. Gueulette, P. Dufour, J.P. Bergerat et P. Bischoff, Rôle de la
protéine BID dans l’apoptose induite par les neutrons rapides dans les lignées lymphoblastoïdes humaines
différant par leur statut p53 (communication orale).
J.M. Denis, P. Bischoff et J. Gueulette, Le Centre d’Expérimentations Radiobiologiques auprès du Cyclotron
de Louvain-la-Neuve (CERCYL) : objectifs, réalisations, perspectives (poster).
131
S. Benzina, B. Fischer, V. Ganasia, P. Dufour, J.P. Denis, J. Gueulette et P. Bischoff, Renforcement, par le
cisplatine, de la cytotoxicité des neutrons rapides sur des lignées lymphoïdes. Etude des mécanismes
concernés (2ème prix ex-aequo du meilleur poster).
-
American Association for Cancer Research (AACR), 94th annual congress, July 11-14, 2003, Washington,
USA
B. Fischer, D. Coelho, S. Benzina, J.M. Denis, J. Gueulette, P. Dufour, J.P. Bergerat et P. Bischoff, Rôle de
la protéine BID dans l’apoptose induite par les neutrons rapides dans les lignées lymphoblastoïdes humaines
différant par leur statut p53. (abstract dans les Proceedings, vol 44, 2nd ed, juillet 2003, p 1228).
-
Computer Based Learning in Science (CBLIS) 2003, July 5, 2003, Nicosie, Chypre
J. P. Soumillion, I. Smits, Th. Delbar, An Organic Chemistry CD-ROM as a multi-use tool for learning or
teaching (proceedings, p.950-954).
-
Direct reactions with Exotic Beams, DREB03, July 10-12, 2003, Surrey, United Kingdom
C. Angulo, Spectroscopy of 5H, 7He, 11N, 12N and 19Na at Louvain-la-Neuve (Talk).
Participant : E. Casarejos
-
Scottish Universities Summer School in Physics: LHC Phenomenology, August 17-29, 2003, St. Andrews,
Scotland
Participants: E. Burton, O. Militaru
-
Workshop on Nuclear Data for the Transmutation of Nuclear Waste, September 2-5, 2003, Darmstadt,
Germany
I. Slypen, E. Raeymackers, S. Benck, N. Nica, A. Koning, J.P. Meulders, V. Corcalciuc, Light-charged
particle production in the interaction of neutrons (En=25-65 MeV) with medium-weight and heavy targets
(talk).
Participant: J.P. Meulders
-
RERMM study progress meeting, September 2, 2003, Toulouse, France
M. Cyamukungu, Presentation of the CSR Technical report on Oersted/CPD data.
-
The 10th International Conference on Ion Sources, 8-13 septembre 2003, Dubna, Russie
M. Loiselet, M. Gaelens, G. Ryckewaert, Development of a 7-Be beam : novel techniques for the ionization
of radioactive metallic elements
M. Gaelens, M. Loiselet, G. Ryckewaert, R.C. Pardo, R.H. Scott, R. Vondrasek, Ph. Collon, W. Kutschera,
Oceans circulation and ECR sources : measurement of the Ar-39 isotopic ratio in seawater
-
The 15th Annual Graduate School of Particle Physics (Joint Belgian-Dutch-German School), September 1526, 2003, Bonn, Germany
Participants : S. Assouak, J. de Favereau, G. de Hemptinne, X. Rouby
-
Seminar on Fission, September 16-19, 2003, Pont d’Oye, Belgium
J. Cabrera, Th. Keutgen, Y. El Masri, V. Roberfroid, I. Tilquin, Ch. Dufauquez, A. Ninane, R. Régimbart,
R.J. Charity, D. Hinde, J.B. Natowtiz, K. Hagel and R. Wada, Fission dynamics with the “Neutron Clock”
using the neutron multidetector DEMON at the Louvain-la-Neuve cyclotron facility, Invited talk (Conference
Proceedings).
-
Radioactive Nuclear Beams 6 Conference, 20-27 septembre 2003, Argonne, Illinois, USA
M. Gaelens, Post-accelerated radioactive beam applications : wear measurements with 7Be
-
The Sixth International Conference on Radioactive Nuclear Beams, RNB6, 22-26 September, 2003, Argonne,
Illinois, USA
C. Angulo, Study of Excited States in Proton-Rich Nuclei from Resonant Elastics Scattering (Invited talk)
-
Second European Summer School on Experimental Nuclear Astrophysics, September 28 -October 5, 2003,
Catania, Italy,
M. Couder, Commissioning of the recoil separator ARES and application to the reaction 19Ne(p,γ)20Na
132
Participant : F. Vanderbist
-
6th Cluster Workshop on the structure and dynamics of the magnetosphere, October 2, 2003, ESTEC/ESA,
Nordwijk, Netherlands
Participant : S. Benck
-
International Workshop on Partitioning and Transmutation and ADS Development, October 6-8, 2003, Mol,
Belgium
E. Raeymackers et al, Light charged emission in neutron induced reactions (En = 25 – 65 MeV) on Bismuth
and Uranium (poster).
J.P. Meulders et al, High and Intermediate energy Nuclear Data for Accelerator Driven Systems (talk).
-
First International Meeting on Applied Physics (APHYS-2OO3), October 14-18, 2003, Badajoz, Spain
Ch. Dufauquez, J. Cabrera, V. Roberfroid, Th. Keutgen, A. Ninane, J. Van Mol and Y. El Masri, Production
of light charged and neutral particles in the proton and alpha induced reactions on natSi target between 20 and
65 MeV, Oral communication (Conference Proceedings).
-
Nuclear Physics in an European Context, 16-17 October, 2003, Ittre, Belgium
C. Angulo, Nuclear Physics with Radioactive Beams (Group Report) (Talk).
E. Casarejos, Study of nuclides 7He and 5H at CRC (Talk).
-
Exotic Nuclei for Nuclear Physics and Nuclear Astrophysics, October 28, 2003, Leuven, Belgium
C. Angulo, Forefront Studies in Nuclear Astrophysics with Radioactive Nuclear Beams (Talk).
M. Couder, Direct measurement of the 448 keV level in the 19Ne(p,γ)20Na reaction
- Third International Workshop on Contemporary Problems in Mathematical Physics, November 1st-7th, 2003,
Cotonou, Republic of Benin
J. Govaerts, On the Road towards the Quantum Geometer’s Universe: an Introduction to Four-Dimensional
Supersymmetric Quantum Field Theories, 12 invited lectures, to appear in the Proceedings.
J. Govaerts, Quantisation and the Cosmological Constant, invited contribution, to appear in the Proceedings.
J. Govaerts, Topological Quantum Field Theories and Pure Yang-Mills Dynamics, invited contribution, to
appear in the Proceedings.
-
RD50 Workshop, CERN, Genève, Suisse, du 3-4 novembre 2003
S. Assouak, E. Forton, A. Furgeri (Karlsruhe), Gh. Grégoire, F. Hartmann (Karlsruhe), S. Freudenstein
(Karlsruhe), Irradiation results on CMS strip sensors with protons and neutrons (Talk).
-
Supersymmetry Days in Hobart, December 10-16, 2003, University of Tasmania, Australia
J. Govaerts, Gauge Symmetry Fixing, BRST Superalgebra and the Cosmological Constant (I and II), invited
contributions.
J. Govaerts, Supersymmetry, Topological Quantum Field Theories and Pure Nonperturbative Yang-Mills
Dynamics (I and II), invited contributions.
-
Brussels Meeting, December 15-16, 2003, Brussels, Belgium
F. Aksouh, D. Smirnov, S. Dean, H. De Witte, J. Gentens, I. Mukha, M. Huyse, O. Ivanov, P. Mayet, R.
Raabe, P. Van den Bergh, K. Van de Vel, J. Van de Walle, P. Van Duppen (IKS, KU Leuven) ; C. Angulo, J.
Cabrera, A. Ninane, P. Demaret (UCL, Louvain la Neuve) ; T. Davinson (Univ. of Edinburgh), Recent results
on the measurement of the 6He β-delayed α + d emission branching ratio.
-
Int. Conference on Physics with forward proton taggers at the Tevatron and LHC, December 2003,
Manchester, United Kingdom
K. Piotrzkowski, High Energy Photon Interactions at the LHC (invited talk).
133
3. Rapports Internes
J. Govaerts, A Parabolic Test of the Constancy of the Velocity of Light, February 2003, 10 pages.
D. Bertrand, Journalistic coverage of the students’ APTOVOL mission during the 6th SPFC: articles published in
regional newspapers and website, collected in an internal press report (July-August 2003).
O. Militaru, K. Piotrzkowski et X. Rouby, et la Collaboration RD39,``RD39 status report’’, CERN-LHCC-2003060.
K. Piotrzkowski et la Collaboration ZEUS, “Search for single-top production in e p collisions at HERA.
(Addendum)”, DESY-03-188.
K. Piotrzkowski et la Collaboration ZEUS, “Search for QCD-instanton induced events in deep inelastic e p
scattering at HERA”, hep-ex/0312048.
K. Piotrzkowski et la Collaboration ZEUS, “Bose-Einstein correlations in one and two dimensions in deep
inelastic scattering”, hep-ex/0311030.
K. Piotrzkowski et la Collaboration ZEUS, “Isolated tau leptons in events with large missing transverse
momentum at HERA”, hep-ex/0311028.
K. Piotrzkowski et la Collaboration ZEUS,“Observation of K0(S) K0(S) resonances in deep inelastic scattering
at HERA”,hep-ex/0308006.
4. Séminaires et séjours de recherche
4.1. Séminaires et cours de 3e cycle
E. Burton (UCL, FYNU) : General method for the numerical computation of one-loop integrals (10/11/2003).
4.2. Séminaires et conférences donnés à l’extérieur
S. Benck, Nuclear data:New needs for new challenges. Study of n-induced light charged particle production
between 25 and 75 MeV at Louvain-la-Neuve, PTB, Braunschweig, Germany (13/02/2003).
K. Piotrzkowski, High energy photon interactions at the LHC, Institute of Nuclear Physics, Cracovie, avril 2003.
K. Piotrzkowski, Production and interactions of high energy photons, colloquium, Polish Academy of Sciences,
Cracovie, mai 2003.
J. Govaerts, Topological Quantum Field Theory and Yang-Mills Dynamics, The School of Physics, University
of the Witwatersrand (Johannesburg, Republic of South Africa) (23/7/2003).
J. Govaerts, Topological Quantum Field Theory and Yang-Mills Dynamics, Institute of Theoretical Physics,
University of Stellenbosch, and the Stellenbosch Institute for Advanced Study (STIAS) (Stellenbosch,
Republic of South Africa) (12/8/2003).
S. Ovyn, D. Bertrand and Gh. Grégoire, APTOVOL, A Parabolic Test Of the constancy of the Velocity Of
Light: Preliminary Results, Invited contribution to the Parabolic Flights Symposium, September 10-11,
2003, ESA/ESTEC (Noordwijk, The Netherlands) (10/9/2003).
K. Piotrzkowski, Luminosity measurement and forward detectors at the LHC, Max Planck Institut, Munich,
Allemagne, octobre 2003.
E. Burton, General method for the numerical computation of one-loop integrals, Invited seminar, Southampton
High Energy Physics Group, University of Southampton (Southampton, England) (14/11/2003).
134
C. Angulo, Application of the elastic scattering technique in nuclear astrophysics and spectroscopy of light
exotic nuclei, Kernfysisch Versneller Instituut (KVI), Groningen, Netherlands (25/11/2003).
F. Guisset, S. Ovyn, G. Pfyffer et V. René de Cotret, APTOVOL ou la Relativité en Apesanteur, Colloque de
Physique, Département de Physique, Université catholique de Louvain (Louvain-la-Neuve, Belgique)
(20/11/2003).
4.3. Séjours de recherche à l’étranger
Th. Delbar, Institut Weizmann, Rehovot, Israël (12-19 /01/2003).
D. Bertrand, 6th SPFC, Bordeaux-Mérignac, France, supervision and journalistic coverage of the students’
APTOVOL mission (15-25/7/2003).
J. Govaerts, The School of Physics, University of the Witwatersrand, Johannesburg, Republic of South Africa
(21-23/7/2003).
J. Govaerts, Institute of Theoretical Physics, University of Stellenbosch, and the Stellenbosch Institute for
Advanced Study (STIAS), Stellenbosch, Republic of South Africa (24/7-16/8/2003).
J. Govaerts, Institut de Mathématiques et de Sciences Physiques (IMSP), et Chaire International de Physique
Mathématique et Applications (CIPMA), Université d’Abomey-Calavi, Republic of Benin (110/11/2003).
J. Govaerts, Honorary Research Staff, The Theoretical Physics Institute, School of Mathematics and Physics,
University of Tasmania, Hobart, Australia (30/11-20/12/2003).
4.4. Divers
G. Ryckewaert, Working Group on the future of the HMI – ISL-facility, Berlin, Allemagne (24/2/2003).
G. Ryckewaert, FINUPHY (Frontiers in Nuclear Physics) – Round Table Meeting, Catania, Sicile, Italie (2728/2/2003).
J. Govaerts, Belgian deleguate on the European Particle physics Outreach Group (EPOG) (Meetings : 45/4/2003, CERN (Geneva, Swtizerland) ; 10-11/10/2003, Vienna (Austria)).
D. Bertrand, C. Delaere and M. Couder, Organization and supervision of a visit at CERN for third year
undergraduate physics students (10-13/4/2003).
J. Govaerts, Member of the Advisory Committee of the Stellenbosch Institute for Advanced Study (STIAS),
Stellenbosch (Republic of South Africa).
J. Govaerts, Co-organizer of the Third International Workshop on Contemporary Problems in Mathematical
Physics, Cotonou (Republic of Benin) (1-7/11/2003).
J. Govaerts, Member of the Advisory Board of the African Summer Theory Institute (ASTI), Cape Town
(Republic of South Africa) (12-30/1/2004).
5. Promotion et Vulgarisation des Sciences
5.1. Campagnes de vols paraboliques de l’ESA
D. Bertrand, J. Govaerts, Gh. Grégoire (Institut de Physique Nucléaire, Université catholique de Louvain,
Louvain-la-Neuve) ; F. Guisset, S. Ovyn, G. Pfyffer, V. René de Cotret (Département de Physique, Université
catholique de Louvain, Louvain-la-Neuve)
135
A consequent part of the work done this year is related to the supervision of a student team selected for
the 6th Student Parabolic Flight Campaign (SPFC) of the European Space Agency (ESA), and the construction
of the experimental set-up with also much competent and efficient help from the mechanical and electronic
shops of the Institute. The purpose of the experiment was a test of one of the major principles of modern physics,
namely the postulate that the speed of light in vacuum c is to be constant independently of the motion, including
an accelerated one, of the reference frame. The experimental set-up was based upon an infrared laser source
whose intensity was modulated at high frequencies (450 MHz). The phase shift between the emitted and received
modulation signals is directly sensitive to a possible variation in the velocity of light as a function of the
acceleration of the reference frame, as occurs indeed for a plane in free fall.
During the campaign, close contacts between the scientific team and belgian press services were
established. After the flights, a preliminary analysis of the recorded data was carried out and the correlation
between the acceleration and the phase angle between emitted and received light beams was closely studied.
Promising results have been presented at the ESA’s Parabolic Flight Symposium on September 10-11, 2003 in
Noordwijk (The Netherlands). Calls have been made to encourage the submission of a professional proposal and
hopefully to future flights. The project has been a great success thanks to the contributions of all involved, as
well as generous financial support from both within and outside the Catholic University of Louvain, including of
course ESA itself.
5.2. Dossiers didactiques
D. Bertrand. S. Bourg, A. Martegani, Electricité, notions de base, dossier pédagogique pour élèves de
l’enseignement primaire et secondaire : cahier du maître et cahier de l’élève.
D. Bertrand, Joëlle Pire-Van Goethem, Plus besoin de fil… le GSM, dossier pédagogique pour élèves de
l’enseignement secondaire supérieur.
D. Bertrand, J. Govaerts, G. Stenuit, Coup de froid sur les électrons : la Supraconductivité, dossier pédagogique
pour élèves de l’enseignement secondaire supérieur.
5.3. Festival des Sciences, Magazine Science Infuse et conférences
D. Bertrand, G. Stenuit and J. Govaerts, Organization, supervision and execution of demonstrations on
superconductivity phenomena aimed at the general public and high school students, on the occasion of
the Science Festival of the Faculty of Sciences, “Festival ScienceInfuse”, March 31 – April 6, 2003.
Th. Delbar, F. Baguet, J.L. Habib: "L'oeil et la vision", Festival des Sciences 2003 (31/3 – 6/4/2003).
V. Depauw, L. Dricot, F. Dufour, X. Rouby and J. Govaerts, Organization and execution of a conference with
demonstrations and video animation aimed at the general public and high school students on the
EQUIMASS experiment flown on the European Space Agency parabolic flight campaign of July
2001, on the occasion of the Science Festival of the Faculty of Sciences, “Festival ScienceInfuse”,
March 31 – April 6, 2003.
Contributions to the Science Awareness Periodical “ScienceInfuse” of the Faculty of Sciences :
D. Bertrand :
- APTOVOL: le défi lancé à Einstein (September 2003)
J. Govaerts :
- Sur la trace des harmonies secrètes de l’Univers (June 2003)
- Quand votre ami Albert fait des mathématiques sans en avoir l’air … (September 2003)
J. Govaerts, Physics Conferences to High-Schools students :
- Institut St. Michel, Verviers (5/2/2003)
- Collège Notre-Dame, Tournai (7/4/2003)
- Collège Notre Dame, Basse Wavre (10/4/2003)
- Collège St. Michel, Bruxelles (8/5/2003)
- Institut Notre Dame, Thuin (23/9/2003)
- Collège Notre-Dame, Gemmenich (16/10/2003)
136
6. Diplômes
6.1. Thèses de doctorat
Vincent ROBERFROID
L’influence de la peau de neutrons sur la compétition entre les mécanismes de fusion-fissuion, fusionévaporaton et transferts très inélastiques dans les réactions 58Ni + 122Sn et 64Ni + 116Sn entre 6 et 7
MeV/nucléon. (défendue le 16 mai 2003) (UCL, Y. El Masri)
6.2. Diplômes d’Etudes Approfondies ou Spécialisées (DEA, DES)
Sami BENZINA Sami, Renforcement, par le cisplatine, de la cytotoxicité des neutrons rapides sur les lignées
lymphoïdes RDM4 et TK6. Etude du rôle de l’apoptose. DEA de Biologie Moléculaire et Cellulaire
(option Physiopathologie et Défenses immunitaires) (Université Louis Pasteur (ULP) de Strasbourg.
Mémoire soutenu en juin 2003)
Dominique BELGE, Etude préliminaire de la fission des actinides (239Pu et 238U) induite par des protons de 22.5
et 62.9 MeV
(UCL, R. Prieels)
Emilie BURTON, Contributions aux corrections de boucles de quarks à la production de bosons de jauge au
LHC
(UCL, J. Govaerts)
Christophe DELAERE, Recherche d'un boson de Higgs entre 100 GeV et 200 GeV auprès des expériences
ALEPH et CMS
(UCL, V. Lemaître)
Joël MARTINEZ MARTINEZ, Topologie et quantification en théories de jauge à basses dimensions
(UCL, J. Govaerts)
Xavier ROUBY, Etudes préliminaires à la fabrication de prototypes de pots romains pour la physique des
interactions entre deux photons à CMS
(UCL, K. Piotrzkowski)
6.3. Mémoires de Licence
Nicolas GHISLAIN : Etude de la production de monojets produits par interaction e+e- dans l’expérience
ALEPH
(UCL, V. Lemaître)
Laurence KOOT : Etude de la production de Higgs légers au moyen du système de sélection en ligne
multileptonique de l’expérience CMS
(UCL, V. Lemaître)
7. Personnel
7.1. Institut de Physique Nucléaire
Personnel académique et scientifique
A. Abdelgafour, étudiant libre
S. Assouak, boursière SCO
D. Belge, étudiant libre (jusqu’au 31/8/2003)
S. Benck, chargé de recherche ESA/PRODEX (à partir du 1/9/2003)
B. Bertrand, boursier FRIA (à partir du 1/10/2003)
D. Bertrand, assistant de recherche UCL
E. Burton, aspirante FNRS
M. Couder, assistant de recherche IISN
M. Cyamukungu, chargé de recherche ESA/PRODEX
J. de Favereau, boursier FRIA
G. de Hemptinne, boursière UCL-FSR
Ch. Delaere, aspirant FNRS
137
Th. Delbar, professeur UCL, responsable de l’Institut de Physique Nucléaire (jusqu’au 31/8/2003)
J. Deutsch, professeur émérite UCL
Ch. Dufauquez, assistant de recherche IISN
Y. El Masri, chercheur qualifié FNRS, professeur UCL, responsable de l’Institut de Physique Nucléiare (à partir
du 1/9/2003)
D. Favart, professeur UCL
A. Ferrant, étudiant libre (jusqu’au 31/8/2003)
E. Forton, assistant de recherche IISN
J. Govaerts, professeur UCL
Gh. Grégoire, professeur UCL
L. Grenacs, professeur émérite UCL
S. Kalinin, assistant de recherche IISN
J. Lehmann, chef de travaux UCL émérite
G. Leibenguth, assistant de recherche PAI (jusqu’au 14/9/2003), assistant de recherche UE (à partir du 15/09/03)
P. Leleux, directeur de recherches FNRS, professeur UCL
V. Lemaître, chercheur qualifié FNRS, chargé de cours UCL
P. Lipnik, professeur émérite UCL
P. Macq, professeur émérite UCL
J. Martinez-Martinez, assistant de recherche UCL (jusqu’au 30/9/2003)
J. El Bachir Mendy, boursier postdoctoral Agence Universitaire de la Francophonie (AUF)
(du 1/10/2003 au 31/7/2004)
J.-P. Meulders, professeur UCL
O. Militaru, boursière post-doctorale UCL
Fl. Payen, aspirant FNRS
K. Piotrzkowski, professeur UCL
R. Prieels, professeur ordinaire UCL
E. Raeymackers, assistant de recherche UCL
V. Roberfroid, assistant UCL
X. Rouby, assistant de recherche UCL
I. Slypen, assistante de recherche UE
I. Smits, assistante de recherche UCL 50 % (jusqu’au 31/8/2003)
G. Stenuit, assistant de recherche IISN
O. van der Aa, boursier FRIA
F. Vanderbist, assistant de recherche IISN
J. Vervier, professeur émérite UCL
Personnel administratif et technique
Administration
L. Kruijfhooft
J.P. Page
G. Tabordon
Ch. Thielens-Lengelé
Bureau de dessin
E. Lannoye
Electronique
L. Bonnet
B. de Callataÿ
M. Jacques (50 %)
D. Michotte de Welle
Th. Quériat (50 %)
Informatique
F. Boldrin
Th. Keutgen (à partir du 1/1/2003)
138
Y. Longrée (jusqu’au 30/4/2003)
A. Ninane
Mécanique
W. Binon (responsable)
J.-M. Delforge
C. Félix (à partir du 13/1/2003)
D. Hougardy
Techniciens de groupe
P. Demaret
J. Van Mol
7.2. Centre de Recherches du Cyclotron
Staff
J.M. Colson
M. Loiselet
N. Postiau
G. Ryckewaert
Secrétariat
C. Baras
Groupe Exploitation
J.P. Clare
T. Dretar
P. Jonckman
P. Leclercq
F. Mathy
G. Urbain
J. Viatour
Groupe Projets
C. Angulo Pérez, chercheur qualifié
G. Berger
Th. Daras
B. Florins
M. Gaelens (jusqu’au 31/12/03)
Atelier de Mécanique
R. Bouchonville (à partir du 15/01/03)
Th. Debuck (jusqu’au 30/04/03)
P. Nemegeer
139

2003 CRC/FYNU - CP3 - Université catholique de Louvain

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