Simulation of inductive and electromagnetic effects associated with single and multichannel triggered spark gaps

When breakdown of a pressurized spark gap is initiated by a high power laser, a narrow spark channel is quickly established. In this case, the risetime of the current in the external circuit due to the breakdown of the gap is determined in a large measure by the properties of this spark channel. To study the inductive and electromagnetic effects associated with the channel dimensions and the resulting physical discontinuities, experiments have been conducted using spark gaps where the discharge channel is simulated by a very thin wire. Current risetime measurements for various wire sizes (i.e., spark channel radius), wire position (i.e., on or off axis), and number of wires (i.e., multichanneling) have been carried out. The risetime values thus obtained agree quite well with the laser-triggered, single and multichannel, spark gap results. These results can be qualitatively explained using simple inductive circuits which dramatically underline the inductive character of the breakdown. The significance of these results in revealing the mechanism of spark gap breakdown will be discussed