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ETUDE THEORIQUE ET EXPERIMENTALE DES INSTABILITES BASSES FREQUENCES DANS UN PLASMA EN CHAMPS MAGNETIQUE ET ELECTRIQUE CROISES

Abstract : The problem of plasma in magnetic and electric fields crossed is crucial in a number of physical situations, ranging from space weather to more terrestrial processes that are magnetic confinement fusion or Hall propulsion. It is well known that this state is leading to the establishment of flows of matter and energy qualified as abnormal since impossible to explain in terms of conventional diffusion. It has been commonly accepted for several years that this transport is intrinsically linked to the instabilities of the plasma medium and to the turbulence associated with them. In our MISTRAL hot cathode laboratory device, a cylindrical column of magnetized plasma is produced by means of an ionizing electron beam. Under the typical experimental conditions, low frequency instabilities are measured at the same time as plasma transport in the cross-field direction, in the shadow of the limiter. The triggering and characteristics of these instabilities are directly related to the establishment of a transverse electric field closely conditioned by the current balance. By means of several diagnostics (probes, intensified camera, laser-induced fluorescence) we have been able to characterize in great detail the situation where a regular mode is developing and the conditions of its transition to a turbulent state. The theoretical analysis carried out in this manuscript shows that the influence of the inertial forces on the ionic fluid experiencing E × B rotation, in particular with the strong E/B value obtained on our device, is determining as well for the equilibrium of the plasma as its stability. It appears in particular that a centripetal electric field global instability similar to that of Simon-Hoh - since linked to a differential drift charged species under the effect of inertial damping - is excited. These results provide a very probable explanation for the experimental observations obtained on our device, although a consideration of the kinetic effects appears essential to confirm it. But beyond our experiences, they hopefully provide an insight into the more general question of crossed fields plasma stability.
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Steve Jaeger. ETUDE THEORIQUE ET EXPERIMENTALE DES INSTABILITES BASSES FREQUENCES DANS UN PLASMA EN CHAMPS MAGNETIQUE ET ELECTRIQUE CROISES. Physique des plasmas [physics.plasm-ph]. Aix-Marseille Universite, 2010. Français. ⟨tel-01857727⟩

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