PREBREAKDOWN LIGHT-EMISSION AND CURRENT PULSES IN LIQUID-NITROGEN

Prebreakdown light emission phenomena and current pulses in liquid nit rogen under positive and negative impulse voltages of both polarities were simultaneously observed. Two structures of light emission, bush-l ike and filamentary, were observed in both polarities. The light pulse s could be classified into a few patterns. A close relation between th ese 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 stepwis e manner. The prebreakdown current pulses occur prior to the correspon ding light pulses, and the time difference between them is 40ns for bo th polarities. From the results of these observations, the mechanisms that cause the difference of the light emission structures is consider ed. For the negative polarity, the structure is determined by the puls e activity after the initiation of the phenomena. In contrast, the str ucture is already determined at the instance of the initiation for the positive polarity.