Prebreakdown Light Emission and Current Pulses in Liquid Nitrogen

Abstract

Prebreakdown light emission phenomena and current pulses in liquid nitrogen under positive and negative impulse voltages of both polarities were simultaneously observed. Two structures of light emission, bush-like and filamentary, were observed in both polarities. The light pulses could be classified into a few patterns. A close relation between these patterns and the structures of the light emission was found. From the streak photographs using the image converter camera, it was found that light emission appears intermittently and propagates in a stepwise manner. The prebreakdown current pulses occur prior to the corresponding light pulses, and the time difference between them is 40 ns for both polarities. From the results of these observations, the mechanisms that cause the difference of the light emission structures is considered. For the negative polarity, the structure is determined by the pulse activity after the initiation of the phenomena. In contrast, the structure is already determined at the instance of the initiation for the positive polarity.