Improved confinement of screw pinch plasma in SPICA 2

SPICA II is a toroidal screw-pinch device, built to study the confinement and stability properties of plasmas having a highly elongated minor cross-section and a current density profile that is much broader than the pressure profile. This particular configuration is produced by applying a fast-rising toroidal fiels B-T to, and inducing simultaneously a toroidal plasma current I-P-L in, a partially ionized gas. After the shock formation, B-T and I-p-l- are (actively) crowbarred to study the evolution of the plasma. Scince the first report onm SPICA II results the main circuits and the preheating system have been modified in such a way that now each discharge can be routinely passively crowbarred, with a decay time of 0.35 ms, leading to reduced plasma-wall interaction prior to and during the main discharges. (author). 4 refs.; 4 figs