Laser-triggering of spark gap switches

Abstract

Switching time jitter is one of the important properties to consider when selecting a closing switch for a pulsed-power system, and the most time-precise triggering can be achieved by the use of lasers. For a mid-gap laser-triggered spark gap, three different physical mechanisms can be used: nonresonant multiphoton ionization, resonant-enhanced multiphoton ionization and electron tunneling. The first one is tradition all y used, whereas the latter two are more exploratory. In this work, the traditional method is employed to study the delay time and time jitter of a laser-triggered spark gap using a Nd:YAG laser at 1064 nm and 532 nm, where the laser pulse is guided via an optical fibre to the spark gap; the laser pulse energy and the applied voltage have been varied for different working gases. One draw-back of the current laser triggering technology compared to other triggering techniques is that laser systems are more complex and prone to electromagnetic interference. Another downside is that the pulse-repetition rate is poor. A discussion about the development of lasers to overcome these issues is included, together with a deliberation about the pros and cons of the two exploratory methods of laser triggering.