Optical observations of discharges across dielectric surfaces in vacuum and in SF6

Any electrode system immersed in an insulating medium must invariably involve solid insulators in some part of the supporting structure. When an electric stress is applied to the electrodes, the solid dielectric fails by a surface flashover along the dielectric. At stresses much below the flashover stress, glows or incipient discharges occur. Optical observations of these early discharges in high vacuum and SF6 environment, using a high speed image intensifier/converter camera, are reported below.