Observation of DC Prebreakdown Phenomena in Dielectrics for Nanosecond Duration Using the Long Image Guide Scope

Abstract

The observation technique for dc prebreakdown in dielectrics was established by the use of a long image guide scope as an image delay line. We observed prebreakdown images in a silicone-oil/PET-film composite under point-cathode/plane-anode. When the photographed duration of images was set below a few nanoseconds, a faint light emission appeared near the anode which was covered by PET film. This result supports the assumption that a complete breakdown is caused by a positive streamer which propagates from the film breakdown spot to the point-cathode.