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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