Magneto-HydroDynamic activity and Energetic Particles - Application to Beta Alfven Eigenmodes - Physics > Plasma PhysicsReport as inadecuate




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Abstract: The goal of magnetic fusion research is to extract the power released byfusion reactions and carried by the product of these reactions, liberated atenergies of the order of a few MeV. The feasibility of fusion energy productionrelies on our ability to confine these energetic particles, while keeping thethermonuclear plasma in safe operating conditions. For that purpose, it isnecessary to understand and find ways to control the interaction betweenenergetic particles and the thermonuclear plasma. Reaching these two goals isthe general motivation for the work conducted during the PhD. Morespecifically, our focus is on one type of instability, the Beta AlfvenEigenmode BAE, which can be driven by energetic particles and impact on theconfinement of both energetic and thermal particles. In this work, we study thecharacteristics of BAEs analytically and derive its dispersion relation andstructure. Next, we analyze the linear stability of the mode in the presence ofenergetic particles. First, a purely linear description is used, which makespossible to get an analytical linear criterion for BAE destabilization in thepresence of energetic particles. This criterion is compared with experimentsconducted in the Tore-Supra tokamak during the PhD. Secondly, because thelinear analysis reveals some features of the BAE stability which are subject toa strong nonlinear modification, the question is raised of the possibility of asub-critical activity of the mode. We propose a simple scenario which makespossible the existence of meta-stable modes, verified analytically andnumerically. Such a scenario is found to be relevant to the physics and scalescharacterizing BAEs.



Author: Christine Nguyen

Source: https://arxiv.org/



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