Formation of a Nanosecond Discharge and Generation of Runaway Electrons When Applying a Voltage Pulse Train

The effect of a pulse repetition rate and a number of voltage pulses on the formation of a nanosecond discharge under a sharply inhomogeneous electric field, as well as on the generation of runaway electrons (REs), has been investigated. Trains consisting of 10, 20, 50, 100, 200, 500, and 1000 voltage pulses were applied across a point-to-plane gap filled with air. The pulse repetition rate was varied in the range of 10–1000 Hz. Waveforms of the voltage and RE current were recorded. Furthermore, the discharge formation dynamics were studied with fast-capturing optical methods. The data obtained were compared with the results obtained for the single mode. It was found that at the pulse repetition rate from 10 to 100 Hz, the amplitude of the RE current pulses decreases monotonously by 3–4 times and stabilizes to the tenth breakdown. The amplitude of the RE current pulses decreases by more than an order of magnitude at the pulse repetition rate of 1000 Hz. The reason is gas heating and a decrease in breakdown voltage. From the point of view of the practical application of the nanosecond discharge, pulse repetition rates up to 100 Hz are most preferable.