Abstract
Alternating magnetic perturbations, generated by external electrodes, are applied to a neutral-beam-heated plasma in the Compact Helical System, to excite stable Alfven eigenmodes (AEs). Resonant peaks in the frequency range of the toroidal Alfven eigenmode (TAE) have been observed in a transfer function defined by the ratio between the magnetic probe signal and the alternating electrode current. The resonant frequency fo agrees well with that of the TAE gap located near the plasma edge, where the strength of energetic ion drive of AEs will be sufficiently low. The damping rates γ derived from the width of the resonant peak are fairly large, i.e., γ/(2π fo) ∼ 20%.
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