Existence of weakly damped kinetic Alfven eigenmodes in reversed shear tokamak plasmas

摘要

A kinetic theory of weakly damped Alfven eigenmode solutions strongly interacting with the continuum is developed for tokamak plasmas with reversed magnetic shear. It is shown that finite Larmor radius (FLR) effects are required for global eigenmode solutions. FLR effects induce multiple kinetic subeigenmodes and collisionless radiative damping. The theory explains the existence of experimentally observed Alfvenic instabilities with frequencies sweeping down and reaching their minimum (bottom).