The toroidal theta pinch in M-and-S configuration

For certain toroidal closed surfaces (M-and-S surfaces) of a β = 1 plasma without resultant azimuthal currents, theory predicts equilibrium. We have produced a toroidal plasma by means of a toroidal theta pinch discharge ( B max = 10 kG, frequency of main discharge, 30 kHz). By adding periodic, additional windings we corrugate the azimuthal field and thus approach M-and-S surfaces. Smear-camera and image-converter investigations of discharges in helium and hydrogen show that in approaching the theoretical surface we approximate equilibrium. This could be observed over time intervals more than three times as long as the drift time in a purely azimuthal field under otherwise identical conditions. The electron densities are in the range of 10 15 to 10 17 cm −3 , the temperature 5 to 10 eV and beta ( β ) between 0.1 and 1.