Experimental Studies of Linear High Beta Heliac Plasma Configurations.

The formation and quasiequilibrium of a high beta heliac plasma is investigated in the High Beta Q Machine, a linear l = 1 stellarator with internal current carrying conductor (hardcore). We vary the rise time of the hardcore current from 9 mu sec to values comparable with that of the main compression fields (450 nsec), adjusting the relative starting time of the two circuits. Flux contour mapping and plasma pressure balance calculated from internal magnetic field probe data is used to distinguish between nearly axisymmetric plasma confined near the hardcore conductor and helically symmetric plasma confined near the heliac magnetic axis. Other parameters calculated from the magnetic field data are the rotational transform and magnetic well depth, which are important factors in the favorable expectations for heliac stability.