Instabilities of the Alfvén eigenmodes (AEs) that can be driven bycirculating energetic ions in optimized stellarators of theWendelstein line (Helias configurations) are considered. It isstressed that the Alfvén instabilities in stellarators mayconsiderably differ from those in tokamaks because specificAlfvén eigenmodes and specific resonances of the wave-particleinteraction appear when magnetic configurations arenon-axisymmetric. An important role of the continuum damping inlow-shear stellarators is revealed. Aimed to calculate thecontinuum damping, a set of resistive magnetohydrodynamic (MHD) equations, whichgeneralize the ideal MHD AE equations obtained in Kolesnichenko et al (Kolesnichenko Ya.I. et al 2001Phys. Plasmas8 491), is derived. The derived equations are solvednumerically to investigate the damping of the AEs of global character in a Helias reactor.
Active control of Alfvén eigenmodes in magnetically confined toroidal plasmas