Preionization for a high beta toroidal device

A report is presented on the optimization of the capacitor discharge preionization of the Columbia Torus 1 Belt Pinch. It is found that the level of ionization achieved in the first pulse of the capacitor discharge could be increased substantially by provision of a large number of well-distributed free electrons before the onset of plasma current. The capacitor discharge itself is optimized to give maximum ionization levels and low impurity content by appropriate choices of electric and magnetic fields and discharge timing. The Belt Pinch dynamics and temperature are found to be strong functions of the preionization, pointing to the benefits of optimizing this aspect of the experiment. (author)