TRANSPORT OPTIMIZATION AND MHD STABILITY OF A SMALL ASPECT RATIO TOROIDAL HYBRID STELLARATOR

A class of small aspect ratio (A) stellarators is found that does nut rely on quasisymmetrization to achieve goad confinement. These systems depart from canonical stellarators by allowing a small net plasma cur rent. An optimization procedure with bounce-averaged omnigeneity and o ther desirable physical properties as target criteria is described and applied to show the existence of a compact plasma device haring A les s than or equal to 3, high beta (ratio of thermal energy to magnetic f ield energy), and low plasma current. The added design flexibility aff orded by the plasma current leads to an attractive low-A hybrid device which is stable to magnetohydrodynamic ballooning modes for (beta) < 6%.