PFL Output Switch Options for Gamble III

NRL is exploring options for the pulse-forming line (PFL) output switch on the Gamble III generator
¹
, currently in design. The Gamble I and II series of generators were the first terawatt scale machines in the Western world to employ water for energy storage
²
and although ubiquitous now, it was originally unclear whether this was a good idea, hence the name “Gamble”. Gamble III will continue with the use of water for the intermediate store (IS) capacitors and the pulse forming line (PFL) output. However, to increase reliability, we aim to improve both the IS (between IS and PFL) switch and PFL output switch. We have already decided to replace the self-breaking water IS switch of Gamble II with three laser triggered gas switches, similar to those used on the much newer Mercury
³
generator at NRL. However, experiments are needed on Gamble II to determine whether the self-breaking oil switch
⁴
used on Gamble II can be replaced with a combination of self-breaking water PFL switch and self-breaking water prepulse switch, in a similar way as is done in Mercury. This paper will detail the design of water PFL and prepulse switches and the results from testing this new hardware on Gamble II generator. These tests are done to better inform the design of these switches for Gamble III and, ultimately, the choice between water and oil for the PFL switch medium.