Beta-induced Alfven-acousti Eigenmodes in NSTX and DIII-D Driven by Beam Ions
Authors: N.N. Gorelenkov, M.A. Van Zeeland, H.L. Berk, N.A. Crocker, D. Darrow, E. Fredrickson, G.-Y. Fu, W.W. Heidbrink, J. Menard and R. Nazikian
Abstract:
Kinetic theory and experimental observations of a special class of energetic particle driven instabilities called here Beta-induced Alfven-Acoustic Eigenmodes (BAAE) are reported confirming previous results [N.N. Gorelenkov H.L. Berk, N.A. Crocker et. al. Plasma Phys. Control. Fusion 49 B371 (2007)] The kinetic theory is based on the ballooning dispersion relation where the drift frequency effects are retained. BAAE gaps are recovered in kinetic theory. It is shown that the observed certain low-frequency instabilities on DIII-D [J.L. Luxon, Nucl. Fusion 42 614 (2002)] and National Spherical Torus Experiment [M. Ono, S.M. Kaye, Y.-K M. Peng et. al., Nucl. Fusion 40 3Y 557 (2000)] are consistent with their identification as BAAEs. BAAEs deteriorated the fast ion confinement in DIII-D and can have a similar effect in next-step fusion plasmas, especially if excited together with multiple global Toroidicity-induced shear Alfven Eigenmode (TAE) instabilities. BAAEs can also be used to diagnose safety factor profiles, a technique known as magnetohydrodynamic spectroscopy.
__________________________________________________
Submitted to: Physics of Plasmas
__________________________________________________
Download PPPL-4388 (pdf 208 KB 20 pp)
__________________________________________________