Fast switching with laser-generated continuous plasma columns

A novel approach to laser triggering of spark gaps is proposed. The method is based on switch initiation by Besselian laser beams. This results in the fast generation of a continuous conducting plasma column(s) and almost instantaneous electrical connection of electrodes. Experiments showed excellent performance of a gas-filled coaxial switch triggered with 2 ns laser pulses: 1.5–2.5 ns rise time, approximately zero delay, and 0.2–0.3 ns jitter obtained within a broad operational voltage range of three orders of magnitude. Depending on the type and pressure of the gas used in the spark gap, the experimentally determined laser energy required for triggering ranged from 40 to 500 mJ. It can be further reduced by factor of 5 by optimization of the focusing system. The unique feature of the proposed triggering method is independence of the required driving energy and switching parameters on the voltage applied to the gap in the range from nearly zero up to standoff voltage. Comparison of this approach with previously developed methods is presented. The switch in single- or multichannel modifications can be used as closing or crowbar devices.