科研之友
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摘要
The multiple branches of discrete Alfv,n eigenmodes trapped in the alpha-induced (alpha = -q (2) Rd beta/dr) potential wells due to the pressure gradient and ballooning curvature effects are investigated in advanced tokamak operation regimes with negative magnetic shear. Here, q is the safety factor, beta is the ratio of plasma to magnetic pressures, and R and r are, respectively, the major radius and the radial coordinate along the minor radius direction. Similarly to the case of positive, these eigenmodes experience small continuum damping due to wave energy tunneling that they could be readily destabilized by energetic particles. In the parameter regime of present tokamak experiments with negative magnetic shear, the discrete Alfv,n eigenmodes are shown to be a possible candidate to understand the experimentally observed Alfv,n modes.
