Investigation of UV LEDs for compact back-lighted thyratron triggering

The back-lighted thyratron (BLT), an optically-triggered pseudospark switch, employs high energy (e.g. UV) photons to produce photoelectrons and initiate the breakdown a low-pressure high-power glow discharge. Characteristics of these switches are high-voltage hold-off (>30 kV), high peak current capability, excellent current rise rate (up to 10¹² A/s) and a simple device geometry. It is of interest to develop ultra-compact BLTs with reliable and practical optical triggering systems for applications in compact pulsed power. Recent remarkable advances in ultraviolet (UV) light emitting diodes (LEDs) have potentially enabled new optical trigger schemes for compact BLTs: replace expensive trigger light sources such as lasers or UV flash lamps, and thereby substantially simplify the light-triggered BLT systems, significantly reducing the total switch cost and the BLT system volume. In this work, potential utilization of UV LEDs for BLT triggering is discussed. The photoelectron yields are measured for metal photocathodes illuminated by a 266 nm UV laser with 5 ns duration and at a pressure range typical for BLT operation. The number of photoelectrons needed to generate an avalanche in a switch and initiate breakdown is extrapolated from a BLT-based, electron-beam current measurement.