Design and performance of a new 6.7-MV Laser-Triggered Gas Switch

A system of 36 laser-triggered gas switches (LTGS) serves as the last set of command-triggered switches in the 80-TW refurbished Z accelerator at Sandia National Laboratories (SNL). The system is instrumental in the overall performance of Z and allows for flexibility in pulse shaping for various experimental campaigns. It is desirable to push the operating envelope of the switches to higher voltages and currents to allow for a higher peak power to be delivered to the load while at the same time reducing jitter and pre-fire rate for increased precision and reliability. We have accomplished this with a new LTGS (which we refer to as the C1.1 switch) while keeping the overall switch size consistent with the physical space available. Like previous gas switches [1,2], the C1.1 LTGS consists of laser-triggered and cascade electrode sections. However, the C1.1's cascade section is cantilevered and is not supported mechanically near the trigger section. An insulating rod located within the cascade electrodes (which supports the cascade section mechanically) is scalloped to reduce the likelihood of electrical tracking. Material choice for the center support rod was important due to both the mechanical and electrical requirements placed on this component. Mechanical shock testing of the new switch was performed on a shaker table available at SNL prior to installation on Z. All electrical testing of the improved LTGS was performed on the Z machine. To date, we have accumulated over 120 shots on C1.1 switches without a pre-fire. Runtime statistics are determined after each shot and show that the C1.1 switches are very tolerant to voltage and pressure variations, exhibiting median runtimes of ~37-41 ns with a jitter of <;6 ns (1σ) on similar shots. Details of the design and results of the mechanical and electrical tests are detailed in this manuscript.