High-speed photography of PMMA breakdown under ns pulse voltages

The electrical breakdown process in polymethyl methacrylate for a point-to-plane gap configuration has been studied using an image convertor camera and a nanosecond rectangular HV pulse generator. The propagation velocity of the breakdown channel for positive polarity is estimated to be /spl sim/80 km/s. The velocity is of the same order as that of secondary fast streamers in several hydrocarbon liquids. >