The Effect of Space Charge Induced by an Electron Beam on Spark Gap Operation

An investigation in to the effect of electron-beam (e-beam) induced space charge on the insulating property of a gas in a spark gap is presented. The characteristics of the gas transition from insulator to conductor show strong dependence on the amount and location of the space charge introduced. Investigations of the delay time and the characteristics of the conducting channel have been made. The delay time from the injection of the e-beam to the collapse of the gap voltage ranges from 10-9 to 10-3 s. From open shutter photography, we observe that the character of the conducting channel is quite varied. Dark, diffuse, filamentary, or diffuse followed by filamentary (single or multiple) channels have been observed, depending on the space-charge conditions. The fundamental processes leading to the collapse of the insulating property of the gas for various experimental conditions are discussed.