Fundamental processes in the laser-triggered electrical breakdown of gases: Unconventional geometries

Experimental studies of the laser-triggered electrical breakdown of spark gaps in three nonconventional geometries have been performed. The results of these studies shed new light on the subject of triggered electrical breakdown of gases in general and confirm conclusions we had drawn previously regarding the interaction between the optical beam and the propagating streamer in the conventional laser-triggering geometry (in which the focused beam struck one electrode after passing coaxially through the opposing electrode). In particular, we relate the V-I characteristics of the spark to the triggering conditions and to the system impedance and operating voltage. This relationship defines an upper limit on the initial ionization volume in order to insure prompt collapse of the gap voltage