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

低温下气体放电的机理与室温下直流和交流均匀电场中气体放电的机理基本相同。然而，在非均匀场中，本项目观察和研究了许多不同于室温下的现象.氮气中的负放电从电晕到辉光连续变化。低温下转变电压基本不变，室温下转变电压略高，可能是由于水蒸气的存在.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.当针尖较尖时，在氮气中的正闪络电压随温度的降低而增大。而针尖等效半径越大，其增长率越小。当半径大于2mm时，闪络电压不随温度变化.空气中的正闪络电压不受温度的影响。对于针尖等效半径大于0.5mm的针头。空气中的正闪络电压在低温下降低，如果超导材料将在较高温度下使用，其中氮气蒸发，这些结果将具有更重要的意义。

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.