Properties of Alfven Eigenmodes in the TAE range on the National Spherical Torus Experiment-Upgrade
Authors: M. Podesta, N.N. Gorelenkov, R.B. White, E.D. Fredrickson, S.. Gerhardt and G.J. Kramer
Abstract:
A second Neutral Beam (NB) injection line is being installed on the NSTX Upgrade device,
resulting in six NB sources with di erent tangency radii that will be available for heating and
current drive. This work explores the properties of instabilities in the frequency range of the Toroidal
Alfven Eigenmode (TAE) for NSTX-U scenarios with various NB injection geometries, from more
perpendicular to more tangential, and with increased toroidal magnetic eld with respect to previous
NSTX scenarios. Predictions are based on analysis through the ideal MHD code NOVA-K. For the
scenarios considered in this work, modi cations of the Alfven continuum result in a frequency upshift
and a broadening of the radial mode structure. The latter e ect may have consequences for
fast ion transport and loss. Preliminary stability considerations indicate that TAEs are potentially
unstable, with ion Landau damping representing the dominant damping mechanism.
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Published in: Physics of Plasmas 20, 082502 (2013) ; http://dx.doi.org/10.1063/1.4817277
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