Firing characteristics of a triggered vacuum gap employing a dielectric coated with a semiconducting layer

Abstract

Some electrical properties of a triggered vacuum gap (TVG) incorporating five different dielectric materials coated with a semiconducting layer to produce a low surface resistance are studied. The dielectric materials used are high-alumina ceramic, steatite ceramic, barium titanate, silicon carbide, and boron nitride. It has been found that the probability of firing and the time delay to firing of such a TVG are practically independent of the substrate material. The time delay to firing generally decreases with an increase of both the trigger energy and the trigger voltage until saturation is reached. The minimum trigger voltage for successful firing is about 300 V for all substrates except for barium titanate which is higher at 700 V. The higher trigger voltage in the case of barium titanate is attributed to the difficulty of coating this material evenly with the particular semiconducting layer used of colloidal solution of aquadag carbon. A new method is described to rejuvenate a TVG which ceased to operate by applying a ’’keep-alive’’ direct current superimposed on the trigger pulse voltage. A mechanism responsible for this phenomenon is also discussed.