Effects of Laser Triggering Parameters on Runtime and Jitter of a Gas Switch

Abstract

Parameters affecting the runtime and jitter of a laser triggered gas switch have been studied. Experiments tested a variety of switch parameters including percentage of selfbreak and switch pressure. The effects of laser beam parameters were also considered, including focal length, laser energy, laser spark length, and laser wavelength. Experiments were performed on the Tiger pulsed power machine. Measurements were taken on a spark gap switch built from the trigger section of a Rimfire switch. A Marx bank consisting of 32, 3.1 uF, capacitors that fed into a 7 nF intermediate storage capacitor was used to drive the switch into a 4 Ω resistive load. The test switch was pressurized to 306 kPa (30 psig) with SF 6 and operated near 1 MV. A New Wave Tempest Nd:YAG laser was used to trigger breakdown of the switch. The laser was focused at the mid-gap between the switch electrodes using lenses with focal lengths between 30 cm and 100 cm. Focused laser energy in the switch ranged from <5 mJ to 80 mJ. The effects of switch and laser beam parameters on the runtime and jitter of a laser triggered gas switch are presented. The end goal of the research is to determine optimal conditions for improved switch performance.

High-reliability 50-kV switch with 532-nm laser triggering

“…For megavolt switches with large gaps, t sw and σ sw are minimized when the length of the laser induced plasma filament approaches the electrode separation [9], implying the existence of an optimum f/# for a specific switch geometry. Even for this small-gap switch, a longer focal length lens (f/8) produces superior results as shown by the data in Table II.…”

Laser Triggering of Spark Gap Switches

“…The spark gap has been axially triggered in several studies [11], [12], [14], [15], whereas [13] used radial triggering as they studied the effect of voltage rise time. This paper presents a testbed and a study of a laser-triggered spark gap where the laser pulse is guided via an optical fiber to the spark gap which is radially triggered and is subjected to a constant voltage [16]- [18].…”