Abstract
In the CHS heliotron/torsatron two types of MHD instabilities excited by the presence of energetic ions are observed during neutral beam injection heating. One is Fishbone-like burst modes (FBs) and the other is toroidal Alfven eigenmodes (TAEs). FBS of m=3/n=2 (m, n: poloidal and toroidal mode numbers) induce pulsed increase in energetic ion loss flux. FBs of m=2/n=1 often induce the saw-tooth oscillations. TAEs with n=1 and n=2 are excited only when the beam velocity exceeds about half of the central Alfven velocity and the net plasma current is induced by NBI to be in the required range. The observed TAEs are localized in the plasma core region where the magnetic shear is appreciably reduced by the net plasma current.
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