Theoretical and experimental study of breakdown delay time in pulse discharge

PIC MCC simulation results on the breakdown in the pulse discharge in helium at pressure of 100 Torr and voltage of U=3.25 kV are presented. The delay of the breakdown development is studied with different initial densities of plasma and excited helium atoms, which corresponds to various discharge operation frequencies. It is shown that for high concentration of excited atoms the photoemission determines the breakdown delay time. In opposite case of low excited atoms density, the ion-electron emission plays a key role in the breakdown development. The photoemission from the cathode is set with a flux of the photons with Doppler shift over the frequency. These photons are generated in reactions between exited atoms and fast atoms. A wide distribution of breakdown delay time was observed in different runs and analyzed.

I. Introduction

In pulse discharges with the operation frequency of 1 – 100 Hz the breakdown delay time after applying the working voltage has stochastic nature. For example, in helium pulse discharge at gas pressure of 100 Torr the breakdown delay time varies from 0.1 to 10 microseconds. The mechanism responsible for the discharge current evolution is still not clear. In this study in PIC MCC simulation we study the evolution of discharge current for different initial plasma conditions. The discharge operates at voltage U=3.25 kV and gas pressure P = 100 Torr.