Study of high-beta plasmas in a helical system

Recent experiments in LHD have demonstrated reactor-relevant high β plasmas. The high beta state with the volume averaged beta of 5 % has been maintained for longer than 100 times the energy confinement time without any disastrous instability. Accumulated data and extended knowledge is a firm basis for a reactor assessment as well as comprehensive physics understanding of high β plasmas. This article addresses highlighted issues from the latest experimental observations in the LHD experiment, which are related to reconfirmation of gaps in non-dimensional parameters, characteristics of growth of MHD instabilities, effects of stochastic magnetic field and resonant magnetic perturbation, and transport associated with a resistive interchange mode. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)