Experimental And Analytical Study Of Laser-triggering In The Rimfire Switch

Abstract

The Rimfire multi-stage gas switch is a low-jitter switch that was developed to meet high-voltage and low-jitter requirements for the PBFA-II pulsed power accelerator. The first stage is laser-triggered. Streak and framing camera data have been collected to determine the closure time, jitter, and optimum parameters for laser triggering. Three phases of closure are observed: (1) fast discharge phase, (2) channel heating phase, and (3) current conduction phase. Gap closure time and jitter are measured as a function of voltage, laser energy, and focal position. A computer model has been developed with sufficient physics detail to provide good agreement with these data. SF/sub 6/ Boltzmann kinetics, multi-photon laser ionization, and photodetachment are included. The photodetachment rate is shown to be a critical parameter in determining the minimum trigger energy for an undervolted SF/sub 6/ gap. The model gives good agreement with experimental closure times and minimum laser energy requirements.