Four-feedplate operation of ZT-40 with passive crowbars

This report summarizes the measurements made on the ZT-40 reversed-field pinch during the start-up on October 5, 1979, until May 1980, when the power crowbar circuitry became operational. The material contained herein pertains to the operation of ZT-40 with four current feedpoints, passive crowbars, and a nonconducting, high-purity alumina liner. The plasma properties are given for reversed-field pinches obtained either by aided or self-reversal and for nonreversed-field (stabilized) pinches. It is demonstrated that ZT-40 was capable of being ohmically heated to approx. 100 eV electron temperatures during the approx. 0.1 ms rise to peak current. Operation is obtained in which the fluctuations during start-up are observed to decrease later in the discharge, producing quiet periods of approx. 0.1 ms