Onset of self-breakdown in a low-pressure spark gap

Conditions for self-breakdown are studied with a time-dependent one-dimensional model which includes effects of ionization by electrons, ions, and energetic neutrals, charge exchange, secondary-electron emission from the cathode due to impact of ions and neutrals, and backscattering of electrons from the anode. Theoretical predictions for the low-pressure branch of the Paschen curve are reported. Pd scaling is explicitly verified. In addition, the rates for current buildup above the critical pressure are calculated. The relative importance of various physical effects on the onset of self-breakdown are studied.