RIMFIRE: A Six Megavolt Laser-Triggered Gas-Filled Switch for PBFA II

We have developed a new multiple-stage laser-triggered sF 6 spark gap, which has performed well in tests at nearly 6 megavolts and half a megampere. It has survived many hundreds of shots between 5 and 5.7 MV the highest voltage tested. A 25 millijoule ultraviolet laser pulse arriving in its trigger gap reliably closes the whole switch in 20 nanoseconds with 0.4 ns 1-sigma jitter. The closing time has a low dependence on the applied voltage, about 0.9 ns/% of self-break voltage. For a 10 mJ laser pulse, the jitter is 1.5 ns and the slope is 1.0 ns/%. No prefires have occurred; the estimated prefire rate at 90% of self-breaking voltage is less than 0.1%. The switch inductance is 400 nanohenries, of which about 100 nh comes from the spark channels. The switch is 68 em long and 61 em in diameter. See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science. Held in San Francisco, CA on 16-21 June 2013. U.S. Government or Federal Purpose Rights License.