La soutenance publique a eu lieu le 20 Novembre 2013 à 13h30,

à la Faculté des Sciences et Techniques de Vandœuvre,

devant le jury composé de :

Dr. Steve Wukitch                             Rapporteur                     MIT/PSFC

Pr. Jean-Marie Noterdaeme                Rapporteur                     Université de Gent

Dr. Pascal Chabert                            Examinateur                   Ecole Polytechnique, Palaiseau

Dr. Kristel Crombe                            Examinateur                   Ecole Royale Militaire, Bruxelles

Dr. Xavier Litaudon                           Examinateur                   CEA/DSM/IRFM

Pr. Stéphane Heuraux                       Directeur de thése           Université de Lorraine

Dr. Laurent Colas                             Co-directeur de thése       CEA/DSM/IRFM

Pr. Bruno Despres                            Invité                              Université Paris VI

Dr. Patrick Joly                                Invité                              INRIA, Palaiseau

A correct understanding of the interactions between the edge plasma and the ion cyclotron (IC) waves (40 - 80 MHz) is needed to inject reliably large amount of power required for self-sustainable fusion plasmas. These thesis objectives were to model separately, with Comsol Multiphysics, but in compatible approaches the wave coupling and the RF sheath formation to anticipate development of a single code combining both.

Modelling of fast wave coupling requires a detailed description of the antenna (2D or 3D) and of the plasma environment by a full wave approach for a cold plasma. Absorption of outgoing waves is emulated by perfectly matched layers, rendered compatible with a plasma dielectric tensor. The code was compared to experimental coupling resistance values of Tore Supra antennas to investigate the necessary sophistication for the geometry description. Experimental trends are qualitatively reproduced but the coupling efficiency is overestimated, most probably due to uncertainty of the real evanescence length of IC waves.

In parallel a novel self-consistent description, including RF sheaths, of the interplay between the cold wave propagation and DC biasing of the magnetized edge plasma of a tokamak was developed with the minimum set of physics ingredients. For Tore Supra antenna cases, the code coupled with TOPICA allowed to unveil qualitatively some unexpected observations on the last design of Tore Supra Faraday screens whose electrical design allegedly minimizes RF sheaths. From simulations, a DC current transport appears necessary to explain the radial structures of measurements. Cantilevered bars have been identified as the design element in the antenna structure enhancing the RFsheaths magnitude.

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