Quasi-Symmetry in Stellarator Research 2. New Trend of Helical System Research

Abstract

New trend is described on the basis of previous and on-going achievements. Magnetic shear is effective to stabilize ideal interchange modes, on the other hand magnetic well is needed for stabilization of resistive modes and micro-instabilities. Owing to recent developments in numerical tools on optimization of magnetic surface quantities it is now possible to construct magnetic surfaces that can satisfy requirements from reactor considerations. Confinement improvement and divertor capability might be an important theme in the near future.