Potential distribution measurement of positive surface streamer by using Pockels device

A new method is developed for directly measuring the transient potential distribution of surface discharge. The measuring system consists of a BGO Pockels crystal, an Ar ion laser, a beam expander, a streak camera and a CCD camera. The potential profile of a positive surface streamer along a linear path of 50 mm in length is measured with high space and time resolution: 0.1 mm and 2 ns in minimum resolution. The electric field component parallel to the direction x of the streamer propagation (E_x) is easily computed from the potential profile. E_x in a positive surface streamer is around 8~10 kV/cm. The potential profile across a positive streamer is also measured. The diameter of a positive streamer is estimated to be about 600 μm