Mechanism of Gas Discharge at Cryogenic Temperature in Non-uniform Field

在直流和交流电压的均匀场中，气体在低温下放电的机理与室温下几乎相同。然而，在非均匀场中，本项目观察和研究了许多不同于室温的现象。氮气中的负放电从日冕到辉光连续变化。转换电压在低温下没有变化，在室温下显示出更高的值，可能是由于水溶液的作用。当气体密度保持不变时，空气中的负放电不受温度变化的影响。在氮气中，当针电极尖端较锋利时，正闪络电压在较低的温度下增加较多。随着针尖等效半径的增大，增大的速率逐渐减小。对于大于2mm的半径，闪络电压不随温度变化。对于尖针，空气中的正闪络电压不受温度的影响。针尖等效半径大于0.5mm的针尖，低温时空气中的正闪络电压降低。如果超导材料将在更高的温度下使用，那么这些结果将更加重要，在更高的温度下，氮气会汽化。

Mechanism of gas discharge at cryogenic temperature is known as almost same as that at room temperature in uniform field for DC and AC voltage. In non-uniform field, however, many kinds of phenomena which are different from those at room temperature have been observed and investigated in this project.1. Negative discharge in nitrogen gas varies continuously from corona to glow. The transition voltage does not change at cryogenic temperature and shows some higher value at room temperature, probably because of aqueous vapor.2. Negative discharge in air is not affected by temperaturechange, when the gas density is kept constant.3. The positive flashover voltage in nitrogen gas increases more for the lowere temperature, when the tip of needle electrode is sharp. However, the increasing rate becomes smaller, when the equivalent radius of needle tip becomes larger. For the radius of larger than 2mm, the flashover volttage does not change by temperature.4. The positive flashover voltage in air is not influenced by temperature for a sharp needle. For the needle whose tip has an equivalent radius of larger than than 0.5mm. the positive flashover voltage in air decreases at low temperature.These results will have more importance, if super-conductive materials will be used at higher temperature, where nitrogen is vaporized.