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Gas/Surface/Laser interactions for fusion devices

par Elodie PICO - publié le

Thesis advisor : Thierry ANGOT
Email and address : thierry.angot, +33 (0)4 91 28 80 19

Co-advisor : Régis BISSON
Email and address : regis.bisson, +33 (0)4 91 28 83 55

Subject description :

The PIIM laboratory is offering a PhD subject in the area of gas/surface interaction for fusion devices of the tokamak type. The PhD work concerns the experimental study of interactions of deuterium and nitrogen atoms and ions with tungsten, the candidate material for the heat and particles exhaust component (divertor) of the International Thermonuclear Experimental Reactor (ITER) under construction near Marseille (Cadarache, France).

The Plasma-Surface group of the PIIM laboratory is pursuing experimental research in three related directions.
1. Fusion fuel (deuterium and tritium) trapping and release from plasma facing materials is one of the most critical issues for ITER and for any future industrial demonstration reactor such as DEMO, because of nuclear regulation issues related to the use of tritium. Understanding the physical process of fuel trapping and release from plasma facing components is therefore of tremendous interest to enable the potential of fusion as an energy source.
2. Nitrogen is envisioned for distributing more evenly by radiation the huge amount of energy directed to the divertor of ITER. However, it remains to be estimated whether the simultaneous presence on plasma facing components of both nitrogen and hydrogen isotopes is compatible and would not become an operational problem i.e. it is important to quantify the surface-assisted production of tritiated ammonia (NH3-xTx) .
3. Laser Induced Desorption is one of the techniques that could be implemented in future fusion devices in order to control the amount of fuel trapped in plasma facing components. Investigations to determine the type of laser exposure to efficiently retrieve the fuel without damaging the reactor component are necessary.

The successful candidate will have access to two ultra-high vacuum (UHV) apparatus allowing the detailed study of deuterium and nitrogen trapping and release in polycrystalline and single crystals of tungsten. These experimental setups allow the in situ preparation of tungsten loaded with deuterium and nitrogen, thanks to several ion sources, neutral radical sources and a plasma implantation chamber. In situ characterization capabilities include Temperature Programmed Desorption (TPD) by mass spectrometry (MS), Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS), High Resolution Energy Electron Loss Spectroscopy (HREELS), to name just some of the available techniques. A 200 W continuous-wave fiber laser allows to study Laser Induced Desorption methods.

We are looking for highly motivated and experimentally skilled individuals with a Master degree (or equivalent) in Physics, Chemical Physics, or related fields. If the Master degree is to be obtained in 2016, a transcript of previous diplomas and master grades will be asked for. Previous experience with mass spectrometry and/or laser techniques and/or UHV techniques is a plus. Applications must include a cover letter, Curriculum Vitae, an abstract of the Master’s thesis, and contacts of at least two scientific referees. Application is to be sent to both Dr. Régis Bisson (regis.bisson and Prof. Thierry Angot (thierry.angot and shortlisted candidates will have to attend an interview at the doctoral school.

The research work will be held in the Plasma-Surface group of the PIIM laboratory at Aix-Marseille University, a dynamic and international group working on the fundamental physics and chemical physics of excited gas/surface interaction relevant to fusion devices and microelectronics. In the fusion area, we are supported by several funding bodies (EFDA-EUROfusion, ANR, “Investissements d’Avenir”) and we collaborate with several labs in France (CEA-Cadarache, CNRS-Orléans, Lille and Paris 13 Universities) and abroad (JSI, Slovenia). It permits to have access to several accelerators facilities to complement our in-house techniques as well as to develop a theoretical modeling of our experiments and an understanding of the fundamental processes into play.

Selected bibliography :

“Dynamic fuel retention in tokamak wall materials : an in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature“, R. Bisson, S. Markelj, O. Mourey, F. Ghiorghiu, K. Achkasov, J.-M. Layet, P. Roubin, G. Cartry, C. Grisolia, and T. Angot, Journal of Nuclear Materials, 476(1):432-438 (2015)

“Characterization of temperature-induced changes in amorphous hydrogenated carbon thin films” C. Hopf, T. Angot, E. Aréou, Thomas Dürbeck, W. Jacob, C. Martin, C. Pardanaud, P. Roubin, and T. Schwarz-Sellinger, Diamond and Related Materials, 37:97 (2013)
“Hydrogen-graphite interaction : experimental evidences of an adsorption barrier”
E. Aréou, G. Cartry, J.-M. Layet and T. Angot, Journal of Chemical Physics 134:014701 (2011)