ZR laser triggered gas switch requirements and performance

The Z machine at Sandia National Laboratories is presently undergoing an upgrade, called Z-Refurbishment (ZR) [1], that is aimed at improving capacity, precision, and capability to essentially all of its pulsed power components, including its thirty six laser-triggered gas switches (LTGS). Voltage and current requirements for the ZR LTGS have increased 25% from the onset of the ZR program, with no allowable increase to the physical footprint (or inductance) for the device. Initial design studies indicated that a total machine peak current of 26 MA could be achieved with the each LTGS operating at 5 MV and 600 kA. Increases in the final design inductance in the transition from vertical water transmission lines to horizontal magnetically insulated transmission lines, higher inductance in vacuum from changes in the load position for improved diagnostic access, and conservatism in the vacuum power flow requirements caused the LTGS operational goal to become 5.4 MV and 750 kA for a total machine peak current of 23 MA in 100 ns to a 10 mm radius, 10 mm long wire array. A comprehensive research program was initiated in August 2005 to improve the performance of the ZR gas switch at the 5.4 MV level, and results of that effort to date are presented herein.