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General information

Reference : UMR6614-THIBES-011
Date of publication : Thursday, June 04, 2020
Scientific Responsible name : Arnaud Bultel et Vincent Morel
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Around 2025, the first plasmas should be produced in the ITER (International Thermonuclear Experimental Reactor) tokamak, currently under construction at Cadarache in the Bouches-du-Rhône. Among the technological challenges that must be resolved in order for this reactor to be fully operational, the in-situ measurement of the penetration within the materials of the reactor wall (Tungsten and Beryllium) of the isotopes of Hydrogen used to carry out the fusion is essential. Indeed, these isotopes can be trapped at very high densities (mole fraction of almost 50%). In addition, the intense neutron flux can also produce a very large number of helium bubbles. These intra-material phenomena can lead to very significant changes in the thermophysical properties of the wall and call its integrity into question, thereby jeopardizing the operational safety of ITER. Only the LIBS (Laser-Induced Breakdown Spectroscopy) technique can meet the challenge of measuring the multi-elemental composition of the exposed walls within the reactor.

In this context, the proposed thesis work aims at preparing the measurement of the content of Hydrogen isotopes and Helium in the walls of a fusion reactor. This preparation is fundamentally based on an experimental phase performed in laboratory, the aim of which is to carry out this measurement by LIBS, in a tokamak type environment, on samples previously prepared and characterized. No activity will be performed directly in tokamak.

In detail, the recruited PhD student will be in charge of preparing and carrying out the experimental phase previously described.

1. Measurement of the spatio-temporal evolution of the electron density and temperature - First, the PhD student will implement the PLEIADES platform of the CORIA laboratory to produce laser-induced plasmas used during the LIBS diagnosis at low pressure (~ 10 Pa) on samples implanted in hydrogen isotopes and helium at CIMAP (UMR 6252, Caen), project partner. He will have to measure the electron density and temperature fields of the plasma and their evolution over time. This determination will be based on spectroscopic analysis of the [120, 800] nm range.

2. Evaluation of the magnetohydrodynamic effects - In a second step, the PhD student will implement visualization techniques by laser shadowgraphy and Schlieren imagery in order to analyze the effect of the magnetic field on the plasma dynamics if the LIBS diagnosis is implemented in these conditions. These experiments will complete the estimate of the differences brought by these tokamak type conditions on the properties of the plasmas produced compared to the usual conditions.

Finally, the PhD student will have the task of analyzing the results highlighted and their communication in newspapers and international conferences in the field.

Work Context

The National Center for Scientific Research (CNRS, Centre National de la Recherche Scientifique) is a public, multidisciplinary research organization under the supervision of the Ministry of Higher Education, Research and Innovation. The CNRS is one of the most important research institutions in the world. To meet the great challenges of today and tomorrow, its scientists explore life, matter, the Universe and the functioning of human societies. Internationally recognized for the excellence of its scientific work, the CNRS is a reference both in the world of research and development and for the general public. The proposed thesis will take place in one of its UMR (Unité Mixte de Recherche, Joint Research Unit) and will be attached to the doctoral school ED 591 PSIME (Physics, Engineering Sciences, Materials, Energy). It will take place at CORIA (Complexe de Recherche Interprofessionnel en Aérothermochimie, Interprofessional Research Complex in Aerothermochemistry) UMR 6614, Saint-Etienne du Rouvray (scientific campus of the University of Rouen-Normandy) in the team “Physico-chemistry of plasma media” under the direction of Dr Arnaud Bultel and Dr Vincent Morel in collaboration with CIMAP (UMR 6252, Caen) and LOMC (UMR 6294, Le Havre).

The team has a complete production and study platform for laser-induced plasmas based on the use of pico- and nanosecond laser sources and the most efficient analytical means in terms of spectroscopy (emission, absorption, fluorescence, scattering) and visualization (shadowgraphy, Schlieren) in time ( 1 ns) and in space ( 3 µm). The team also has all the means for modeling and simulating the dynamics of the plasmas generated and their radiative characteristics.

Constraints and risks

The proposed works are based on the use of class IV laser sources. Training in the dangers, risks and uses of these laser sources must take place before all the experimental work.

Additional Information

The PhD student must hold a master's degree in energy (or an engineering degree) oriented towards optical diagnostics, in particular spectroscopy, with knowledge of laser sources. He will also have to show a clear editorial quality as well as being able to formulate and lead a scientific project, to work in a team while demonstrating autonomy and organizational capacity.

Interested candidates must provide a full CV mentioning two contact persons likely to be contacted by recruiters as a reasoned cover letter.

Deadline for receipt of applications: June 15, 2020

The date of recruitment may be postponed until the end of the confinement period.

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