Investigation of gaseous electron multiplier-based triggering of back-lighted thyratrons

Developing reliable and compact optical triggering systems for back-lighted thyratrons (BLTs), light-activated pseudospark switches, is of interest for compact pulsed power [1]. Investigation of the electron multiplication methods is crucial for utilization of low-intensity light sources, including ultraviolet (UV) light emitting diodes (LEDs) [2], for triggering BLTs . Gaseous electron multipliers (GEMs) whose operation is based on gas multiplication within small, sub-millimeter to millimeter diameter holes as a result of high intensity fields have shown multiplication gains of 10 in both atmospheric and low pressure gas mixtures and noble gases [3, 4] In this work, we investigate a novel optical triggering scheme utilizing magnesium as the photocathode and an internal GEM for electron multiplication for compact BLT switches. Quantum efficiency (QE) of magnesium under BLT relevant pressure conditions (up to 100 mTorr) were measured to be 10⁵ [5]. Higher quantum yield was demonstrated for utilization (with the use) of Mg photocathode compared to Cu and Mo photocathodes. In addition, the electron multiplication gain of a customized GEM in argon was measured to be up to 10². The effect of Mg as a photocathode material on switch performance (delay, jitter) with and without GEMs is also discussed.