Prebreakdown light emission and current pulses in liquid nitrogen

Prebreakdown light emission phenomena and current pulses in liquid nitrogen under impulse voltages of both polarities were observed simultaneously. Both bush-like and filamentary structures of light emission were observed in both polarities. Light pulses observed by a photomultiplier tube could be classified into two patterns, and a relation between these patterns and the structures of the light emission was also discussed. From the streak photographs using an image converter camera, it was found that light emission appears intermittently and propagates stepwise. By compensating the delay times of all signal lines in the experimental system, it was found that prebreakdown current pulses occur prior to the corresponding light pulses, and the time difference between them is approximately 40 ns for both polarities