Abstract
Laser triggered, megavolt, megampere gas switches are frequently utilized to synchronize multiple pulsed power driver modules for inertial-confinement fusion, isentropic compression, and radiation physics experiments. The device developed to synchronize the 36 modules of the refurbished Z accelerator at Sandia National Laboratories is a 5.4 MV, 700 kA, sulfur-hexafluoride (SF6) filled, laser triggered gas switch. At this operating level, switch jitter is 5 ns, the prefire rate is less than 0.1%, the average optic lifetime is greater than 200 shots, and the flashover rate is less than 1%. Over 1000 shots on a single-module test facility were conducted while iterating several potential design improvements, including utilizing low-erosion electrode material, varying SF6 pressure, and modifying internal switch geometry all while keeping the basic switch architecture and footprint constant. Results of this development effort are presented herein.
Highlights
Multimegampere pulsed power drivers for inertialconfinement fusion, isentropic compression, radiation physics, and equation-of-state studies require robust and reliable switching
The laser triggered gas switch that is designed for the refurbished Z accelerator is an evolution of the Rimfire gas switch first implemented on Hermes III [13]
The laser triggered gas switch developed for the refurbished Z accelerator operates at 5.4 MV, 700 kA, using sulfur-hexafluoride as the fill gas
Summary
Multimegampere pulsed power drivers for inertialconfinement fusion, isentropic compression, radiation physics, and equation-of-state studies require robust and reliable switching. Focusing a laser beam to initiate plasma formation, is presently the most reliable way to achieve nanosecond jitter utilizing a compact, off-the-shelf package Synchronization of these systems requires robust and reliable switching whether the operational mode is for maximum energy efficiency in early time (perfect synchronization of all lines) or for pulse shaping (delayed timing of lines to provide specific pulse shape). Published manuscripts discussing multimegavolt gas switches frequently quote a maximum operating voltage for the device These devices achieved this voltage for a limited number of self-closure tests, but acceptable performance could not be demonstrated at this level with reasonable reliability.
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