Electrical Effects of Multichanneling in the 2.5 MV Rimfire Gas Switch using a Laser Trigger

Abstract

The University of Missouri Terawatt Test Stand (MUTTS) has conducted many untriggered experiments on a Rimfire gas switch scaled to 2.5 MV. The focus of these experiments was to evaluate what methods may be used to control the distribution of cascade arcs. The untriggered data indicates that the rise time of switch current does not statistically improve, as expected, as the number of cascade arcs per gap increased beyond two channels. For the same data, the number of arcs in the cascade section more dramatically affects the output current period. This indicates that in late time increased multichanneling has a more pronounced effect than in early time. The switch is triggered with a frequency quadrupled Nd:YAG laser at 30 mJ with a 3-5 ns pulse width. Since the focused laser does not ionize the full length of the trigger section, there is little effect on current rise time when compared to untriggered data, but more channels form in the cascade section for an air filled switch. The cascade section was shorted and data are presented describing the contribution of the single channeling trigger section to overall switch impedance. The electrical effects of multichanneling using a laser trigger, the formation of arc channels in the cascade section, and the implications the results have on the future design of fast gas switches are discussed.