Physics issues of compact drift optimized stellarators

Physics issues are discussed for compact stellarator configurations which achieve good confinement by the fact that the magnetic field modulus \B\ in magnetic co-ordinates is dominated by poloidally symmetric components. Two distinct configuration types are considered: (1) those which achieve their drift optimization and rotational transform at low beta and low bootstrap current by appropriate plasma shaping; and (2) those which have a greater reliance on plasma beta and bootstrap currents for supplying the transform and obtaining quasi-poloidal symmetry. Stability analysis of the latter group of devices against ballooning. kink and vertical displacement modes has indicated that stable beta values on the order of 15% are possible. The first class of devices is being considered for a low beta near term experiment that could explore some of the confinement features of the high beta configurations.