Laser Triggering of Spark Gap Switches

Switching time jitter is an important property to consider when selecting a closing switch for a pulsed-power system, and time-precise triggering may be achieved through the use of lasers. For a midgap 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 traditionally used, whereas the latter two are more exploratory. In this paper, the traditional method is employed to study the delay time and time jitter of a laser-triggered spark gap using an Nd:YAG laser at 1064 and 532 nm, where the laser pulse is guided via an optical fiber to the spark gap; the laser pulse energy and the applied voltage have been varied with nitrogen as the working gas. One draw back of the current laser triggering technology compared with 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.