Influence of electrode gap on breakdown voltages of a multi-gap pseudospark discharge device under nanosecond pulses

Pseudospark-sourced electron beams of high energy can be produced in multi-gap pseudospark devices under high breakdown voltages. The breakdown voltages and the gap separation of the discharge device have been studied. Collisional ionization in the gaps has been semi-quantitatively analyzed. Based on the results, the influence of the electrode gap on the breakdown voltages has been verified. Collisional ionization during device discharge begins initially in the first gap near the cathode. The electrons produced in the first gap move towards the second gap and contribute to the collisional ionization in the second gap. The process proceeds to successive gaps with collisional ionization occurring in all gaps. For wider gap separations, the number of collisional ionizations in the gap is large, and hence, more electrons move through the intermediate electrodes into the posterior gaps. This creates a cascading of collisional ionizations, leading to a decrease in breakdown voltage. The influence of the coefficient of collisional ionization on the whole process in the posterior gaps may be slight under different gap separations, as electrons moving into the posterior gaps are plentiful. The breakdown voltage mainly depends on the first gap separation near the cathode. Published by AIP Publishing.