Potential and charge distributions of positive surface streamer

The fine structure of a surface streamer is investigated by not only a conventional electrostatic probe but also a Pockels sensing system. The Pockels sensing system consists of two optical subsystems: A subsystem for measuring the transient change in the potential distribution along a linear path of 50 mm in maximum length which consists of a continuous Ar ion laser and a streak camera, and the other subsystem for measuring the instantaneous two-dimensional potential distribution on a 25 mm square area which consists of a pulsed laser and a CCD camera. The minimum resolution of the former subsystem is determined by the speed of streak camera, and the later one is the pulse width of the laser. The transient change of the potential distribution along a propagating a positive surface streamer in atmospheric air is measured with this system. From the measured potential profile, the electric field and the charge distributions are also calculated.