Low and high frequency beam ion driven instabilities in the National Spherical Tokamak Experiment (NSTX) plasma were analyzed. Low frequency magnetohydrodynamics (MHD) activities in ∼100 kHz frequency range on NSTX were often observed and identified as the TAEs driven by beam ions. It was shown that there was a large uncertainty in the experimental plasma parameters upon which the numerical model was based for the low-n TAE instabilities. The analysis helps to validate the NOVA/NOVA-K predictions that TAEs will be unstable in ITER if driven by fusion alphas in a plasma with T i0>20 KeV.
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