Abstract
Sensing techniques with a Pockels crystal have been applied to directly measure the potential and electric field distribution of surface discharge creeping on adielectric material. The transient change of potential distribution with a surface discharge, which propagates on a 780 μm thickness BOO crystal in SF6 at 160_??_760 Torr pressure, is measured with high time and spatio resolution by using Pockels sensor, a CCD camera and a streak camera.
Little significant differenceis recognized between the potential distribution along a negative discharge and thatalong a positive one. The distribution of Ex along a streamer has a triangular profile and Ex has its maximum near the head of it. The value of Ex around the streamer head keeps around the critical value for the gas ionization. During subsequent stepwise propagation of the streamer, a leader, whose electrical conductivity is relatively high, is being inside previous discharges.
