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Plasma/Surface/Laser interactions for magnetic nuclear fusion devices

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Thesis advisor : Prof. Thierry ANGOT
Coordonnées : thierry.angot, 04 91 28 80 19
Co-advisor : Dr. Régis BISSON
Coordonnées : regis.bisson, 04 91 28 83 55

Subject description :
The PIIM laboratory is offering a PhD subject in the area of plasma/surface interaction for fusion devices of the tokamak type. The PhD work concerns experimental studies of various atoms and ions bombarding 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 four related directions :
- Fusion fuel (D/T mix, i.e. 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. To do so, we plan to compare the fundamentals of deuterium retention in pristine tungsten versus heavy-ion damaged tungsten (to simulate neutron irradiation resulting from the D/T fusion).
- Nitrogen seeding 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 because of the production of tritiated ammonia. Therefore, we plan to systematically quantify the surface-assisted production of partially deuterated ammonia (ND3-xHx).
- If tritiated ammonia production appears too important, a light rare gas such as Ne is envisioned to be used instead for radiative cooling. However, Ne could affect tritium retention in tungsten. Additionally, the effect of He (the ash of the D/T fusion reaction) on tritium retention needs to be better understood. Thus, we plan to study synergetic interactions of deuterium and rare gases (He, Ne) in tungsten.
- 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 necessary to efficiently retrieve the fuel without damaging the reactor component is desired and we have developed an experimental setup to efficiently test such concepts.
The successful candidate will have access to two ultra-high vacuum (UHV) apparatus allowing the detailed study of one or several of research directions described above. These experimental setups permit the in situ preparation of tungsten, their bombardment with deuterium, nitrogen and rare gases, 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 continuouswave fiber laser allows to study Laser Induced Desorption methods.
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 undamental 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 (EFDAEUROfusion, ANR “Investissements d’Avenir”) as well as ITER (“Ammonia” contract) and we collaborate with several labs in France (CEA/IRFM 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 fundamental processes into play.
Bibliography (selected) :
“Simulations of deuterium atomic exposure of self-damaged tungsten”, E.A. Hodille, A.
Zaloznik, S. Markelj, T. Schwarz-Selinger, C.S. Becquart, R. Bisson, and C. Grisolia, Nuclear Fusion, accepted for publication (2017)
“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 467(1) 432 (2015)
“Reversible Hydrogenation of Deuterium-Intercalated Quasi-Free-Standing Graphene on SiC(0001)“ F.C. Bocquet, R. Bisson, J.-M. Themlin, J.-M. Layet, and T. Angot, Physical Review B, 85(20):201401(R) (2012)