Reversed-field pinch discharge improvement with parallel-connected auxiliary toroidal field coils

Improvements in discharge duration and peak current have been obtained on the Reversatron reversed-held pinch by the addition of auxiliary parallel-connected toroidal field coils. Parallel connection forces the toroidal flux in each coil to be equal. These coils were used without removing or disconnecting the normal series-connected coils. In discharges with the auxiliary coils, F and Theta are unchanged, the plasma resistance is reduced and there is less shot-to-shot variation in the discharges. Diagnostic coils show that field errors with poloidal mode number m=0, and toroidal mode numbers n=6 and n=12 arising from asymmetries in the vacuum vessel are reduced in the setting-up phase. In the sustainment phase, there is a significant reduction in the external kink modes with m=1 and n=3, 4, 5, and 6.