Impact of rotation and kinetic damping on the NSTX ideal-wall limit
POSTER
Abstract
Kinetic resonances have previously been identified to play an important role in the stability of the resistive wall mode (RWM) in high-beta NSTX plasmas operating above the ideal no-wall stability limit. Under such circumstances, the ``plasma mode'' which determines the with-wall limit is typically assumed to be stable. To assess this assumption, systematic kinetic stability analysis of the with-wall limit has been carried out for the first time using the MARS-K code for NSTX. The stability of the plasma mode is found to be a sensitive function of rotation and dissipation. Specifically, calculations indicate that as the rotation is increased to experimental values in the absence of dissipation, the n=1 mode becomes unstable at the experimental nominal wall position of the wall which is inconsistent with experiment. Inclusion of strong parallel sound-wave damping does not substantially change the ideal plasma mode stability. Including perpendicular damping through precession resonances can recover plasma mode stability at high rotation, but only for small plasma-wall gap. Importantly, the inclusion of full kinetic damping model (precession + bounce + transit resonances) can significantly increase plasma mode stability consistent with the experiment.
Authors
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J.E. Menard
Princeton Plasma Physics Laboratory, PPPL
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Yueqiang Liu
Culham Centre for Fusion Energy