Shear Alfven Eigenmodes in compact stellarators

The shear Alfven continuum has been calculated for stellarators of arbitrary shape and aspect ratio using a symmetric matrix form of the continuum equation. Stellarators introduce strong poloidal/toroidal couplings in |B| and the gρρ metric coefficient that can induce new continuum gap structures not present in axisymmetric tokamaks. Low field period (Nfp = 2 - 3), low aspect ratio devices result in strongly coupled toroidal mode families (n = n0, n0 ± Nfp, n0 ± 2Nfp, etc.) that lead to HAE (Helical Alfven Eigenmode) and MAE ( Mirror Alfven Eigenmode) couplings at lower frequencies than are the case for larger aspect ratio, higher field period stellarator devices. Low field period configurations also have a higher density of coupled continua for a given frequency range; this characteristic could lead to higher levels of continuum damping. Copyright (2002) Australian National University- Research School of Physical Sciences and Engineering