Breakdown mechanisms and electrical properties of triggered vacuum gaps

Abstract

Some electrical characteristics of a triggered vacuum gap (TVG) having three different dielectric materials have been studied. Silicon carbide which possesses very high resistance (500 MΩ), steatite ceramic of medium resistance (20 MΩ), and boron nitride of very low resistance (50 Ω) have been used. The resistance of the dielectric is found to decrease with increasing trigger current and this is attributed to the deposition of metal vapor on the surface. The minimum trigger voltage and trigger current nessessary for successful operation of the TVG are measured. Deconditioning (reduction) in the minimum trigger voltage, after repeated firings, has been found and is attributed also to the deposition of metal vapor on the dielectric surface. The minimum trigger current for successful firing of the main gap decreases with increasing trigger voltage. The probability of successful firing of the TVG is found to rise rapidly with increasing trigger voltage. The delay time between the application of the trigger pulse to the breakdown of the main gap decreases with increasing trigger current and trigger voltage. A mechanism is suggested for the operation of the TVG.