Charging of Insulators in a surface Discharge Switch

Surface discharge switches, which have exceptionally low inductance, are of interest for fast switching of electrical energy. This paper describes experimental data on the residual electric field and spatial charge distribution measurements on three insulators, namely, G-10, Delrin, and Lucite used in a surface discharge switch. The insulators were subjected to different numbers of shots in the switch and the measurements were carried out after the applied field was turned off. The G-10 samples exhibit positive charging with 1/e decay times ranging from 3.8 to 7.4 h, and show a great deal of structure in the charge distribution patterns. Delrin specimens exhibit negative charging with considerably longer decay times than those of G-10, and the charge patterns are not well defined. Lucite, on the other hand, shows quite different results, i. e. no detectable charge decay after fifteen hours and no definite charge patterns. The results are qualitatively discussed and are related to the resistivity of the dielectricts and the switch operating characteristics.