Transport Optimization and MHD Stability of a Small Aspect Ratio Toroidal Hybrid Stellarator

Abstract

A class of small aspect ratio (A) stellarators is found that does not rely on quasisymmetrization to achieve good confinement. These systems depart from canonical stellarators by allowing a small net plasma current. An optimization procedure with bounce-averaged omnigeneity and other desirable physical properties as target criteria is described and applied to show the existence of a compact plasma device having A{approx_lt}3 , high {beta} (ratio of thermal energy to magnetic field energy), and low plasma current. The added design flexibility afforded by the plasma current leads to an attractive low-A hybrid device which is stable to magnetohydrodynamic ballooning modes for {l_angle}{beta}{r_angle}{lt}6{percent} . {copyright} {ital 1998} {ital The American Physical Society}