Breakdown probability and influence on breakdown delay

A method for determination of probability of electrical breakdown of gases is presented in this paper and results are compared with theory. The method is based on the measurements of breakdown time delay at different afterglow periods (relaxation times): where the secondary electron yield initiating breakdown is caused by residual active states remaining from the preceding glow. Measurements are carried out at low pd (gas pressure times electrode spacing) of nitrogen and higher overvoltages up to 2.1U(s)(U-s: the static breakdown voltage). The experimentally determined breakdown probability is fitted by theoretical expressions for both the Townsend and streamer model of electrical breakdown, with particular attention to the higher overvoltages. On the basis of our measurements and theoretical fit it can be concluded that the Townsend mechanism is applicable at low pd value over the whole range of overvoltage applied and a value of a secondary emission coefficient for gold-plated copper cathode is obtained. With the decrease of the breakdown probability and electron yield the distributions of delay times become broader and centered at larger delay times, and the positive asymmetry and roundness increase.