Experimental Observation of Surface Charging of High-Voltage Insulators for Vacuum Apparatus

The surface of cylindrical insulators placed in high vacuum becomes positively charged when subjected to a high-voltage stress parallel to the dielectric surface. A study is made of the variation of the surface charge density as a function of the voltage applied to insulators made of alumina ceramic, nylon, Teflon® and Plexiglas®. Direct and pulsed voltages were used in the experiments.