High power plasma opening switch operation on Hawk

The Hawk pulsed power generator is used in plasma opening switch (POS) experiments in the 1-µs conduction time regime to study long conduction time switch physics. Cathode and anode geometries, especially in the switch region, can have a major impact on switch performance. There is a tradeoff between higher voltage and lower conducted current as the radius of the cathode center conductor is decreased Tapering the cathode over the switch length has produced the best performance to date: 0.7 TW at 0.75 µs conduction times with flashboard plasma sources and 1.6 MV has been generated at 1 µs conduction times with cable gun sources. There is a limit on the minimum radial gap in the switch and downstream region below which voltage and current transfer are reduced Switch performance deteriorates as the anode outer conductor just downstream of the switch, but at the same radius as the switch rods, is extended toward the load. As observed in past experiments, POS performance is independent of the plasma source used (flash boards, cable guns, or gas guns) in a given switch/load configuration. A helical center conductor in the switch region, which increases the total insulating magnetic field by a factor of 2.3, resulted in dramatically degraded switch opening for conduction times greater than 0.35 µs.