Dependence of the Delay Time on the Mean Electron Seed Kinetic Energy in a Pseudospark Discharge

The time taken to reach the breakdown phase in a psuedospark discharge is shown to depend upon the mean kinetic energy of the seed electrons. The electrons are injected at the axis on the hollow cavity back wall and the initial electric field across the anode-cathode gap is insufficient to permit or enhance electronimpact ionization throughout most of the hollow cathode backspace. The investigation is performed using the two-dimensional kinetic particle-in-cell code, OOPIC Pro. It is shown that the delay time is dependent upon the energy range of the seed electrons, where two categories are distinguished; (1) mid-energy, where the ionization cross-section decreases after each collision energy loss, and (2) high-energy, where the injection speeds ensure that, in contrast, the cross-section increases after energy losses as the electrons travel downstream to the cathode exit. In the latter case, linear dependencies on the kinetic energy of the seed electrons are demonstrated making it possible to estimate the neutral gas pressure that will minimize the delay time for a given geometrical configuration and mean seed injection speed.