Statistical properties of electrical breakdown in vacuum

The breakdown probability distribution function was determined for DC and impulse voltages, for conditions of gap pressure of 10, 0.1, and 10/sup -4/ Pa and gap length of 0.1 mm. It was found that DC and impulse voltages are associated with different types of probability distribution function due to different initiation mechanisms. The statistical influence of the number of previous breakdowns on the probability distribution of the breakdown voltage was investigated. By applying the U test for analysis of measured data, it was found that at lower gap pressure, the breakdown voltage probability changes after a smaller number of breakdowns than it does at higher gap pressure.