Effect of emission on subnanosecond breakdown in a gas diode at low pressure

The paper presents experimental and numerical research results on the operation of a gas diode at low pressure. A large scattering in runaway electron beam current (from 20 to 100 A) with regard to the average (∼50 А) is observed for a tubular cathode with a working edge radius of 30 μm, nitrogen pressure of 40 mbar, and interelectrode gap of 6 mm. Numerical simulation data show that the low beam current (∼20 A) is due to early electron emission from the cathode (at the stage of low-voltage prepulse) in which the runaway electron beam is formed from the boundary of a plasma layer developed early in the breakdown. The high beam current (∼100 A) is due to delayed electron emission from the cathode, which increases the diode voltage and the runaway electron beam current. In the latter case, the runaway electron beam is formed directly at the cathode.