Offre de Post doc Plasma d`hydrogène en interaction avec des

Pos
Offre de Post doc
Plasma d’hydrogène en interaction avec des surfaces de diamant:
Erosion et production d’ions négatifs en surface
Institution : Aix Marseille University / CNRS
Laboratoire : PIIM, service 241, Centre de St Jérôme, 13397 Marseille Cedex 20
Superviseur : Gilles CARTRY
Téléphone : 33(0)4 91 28 89 59
e-mail : [email protected]
Plus d’information: contacter Gilles Cartry par email
Postuler: Envoyer votre CV par email à Gilles Cartry
The PIIM laboratory (Aix-Marseille University, France) is proposing a two-year post doc position dealing
with plasma-surface interactions for fusion applications. The project is conducted within the
framework of a collaborative project between PIIM laboratory, LSPM laboratory (Paris Nord University,
France), IRFM laboratory (CEA Cadarache, France) and DIFFER institute (The Netherlands). The post
doc will mostly work at PIIM laboratory with possible experimental campaigns at LSPM, CEA and at
DIFFER on Magnum PSI device.
Description of the project
Hydrogen plasma in interaction with diamond materials:
erosion and negative-ion surface production
Introduction:
The ITER project and its successor DEMO (first fusion based power plant prototype) aim at controlling
proton fusion reactions and at producing energy. In these fusion devices, heating and current drive of
the plasma are mainly obtained through the injection of high-energy (1-2 MeV) and high-intensity D/H
neutral beams originating from neutralized D-/H- negative-ion beams. The standard and most efficient
solution to produce high negative-ion current uses cesium (Cs) injection and deposition inside the
negative-ion source to enhance negative-ion surface-production mechanisms. However, ITER and
DEMO requirements in terms of extracted current push this technology to its limits. Diffusion of cesium
inside the accelerator stage of the neutral beam injector (NBI) will complicate the ITER-NBI
maintenance, and will lead to severe issues for long-term operation-stability of DEMO NBI.
Objectives:
The first objective of the present project is to find alternative solutions to produce high yields of H-/Dnegative-ions on surfaces in Cs-free H2/D2 plasmas. It has been shown at PIIM laboratory that carbon
materials are excellent negative-ion enhancer materials. In particular we have shown a huge
enhancement of negative-ion yield on boron-doped-diamond at high temperature. The yield increase
observed places diamond material as the most up to date relevant alternative solution for the
generation of negative-ions in Cs-free plasmas. The project aims at fully characterizing and evaluating
the relevance and the capabilities of diamond films (intrinsic and doped polycrystalline, single crystal
as well as nanodiamond films…) as negative-ion enhancers in a negative-ion source.
The second objective is to investigate diamond erosion under hydrogen (deuterium) plasma
irradiation, with two main motivations. First, material erosion could be a limitation of the use of
diamond as a negative-ion enhancer in a negative-ion source and must be evaluated. Second, the
inner-parts of the tokamaks receiving the highest flux of particles and power are supposed to be made
of tungsten, but its self-sputtering and its melting under high thermal loads are still major issues
limiting its use. It has been shown in the past by one of the partners that diamond is a serious candidate
as an efficient alternative-material for fusion reactors. Therefore, diamond erosion in hydrogen
plasmas will also be investigated from this perspective. At the moment when all the efforts are put on
tungsten, maintaining a scientific watch on backup solutions for tokamak materials is crucial.
Post-doc work:
The work is essentially experimental. The post doc will study negative-ion surface production on
diamond, as well as diamond erosion, in a high-density low-pressure hydrogen plasma source. The
source is equipped with in-situ surface and plasma diagnostics: TALIF (Two photon Absorption Light
Induced Fluorescence) for the measurement of atomic flux, Langmuir probe, mass spectrometry,
ellipsometry, XPS (X-Ray Spectrometry), TPD (Temperature Programmed Desorption)...
Knowledge in plasma science and/or surface science is required. The candidate must have experience
in LIF measurements and surface analyses (preferentially ellipsometry or XPS …).
References:
•A Ahmad, J Dubois, T Pasquet, M Carrère, J M Layet, J B Faure, G Cartry, P Kumar, T Minéa, S
Mochalskyy and A Simonin, Plasma Sources Sci. Technol. 22 (2013) 025006 (15pp)
•G. Cartry, L. Schiesko, C. Hopf, A. Ahmad, M Carrère, J. M. Layet, P. Kumar, and R. Engeln, Physics of
Plasmas 19, 063503 (2012)
•P Kumar, A Ahmad, C Pardanaud, M Carrère, J M Layet, G Cartry, F Silva, A Gicquel and R Engeln, Fast
track communication, J. Phys. D: Appl. Phys. 44 (2011) 372002