Pulsed Nanosecond Breakdown of a Hollow Cathode Discharge With Pseudospark Geometry

This paper reports the experimental results from the appearance of three discharge modes in a special geometry as a function of applied negative voltage pulses. The geometry is a four-gap pseudospark one with a gap distance of 4 mm, a metallic hollow cathode, and an anode. The applied pulsed voltage <inline-formula> <tex-math notation="LaTeX">$U_{p}$ </tex-math></inline-formula> varies from −20 to −80 kV. The pulse shape is a rectangular one with a pulsewidth of 50 ns and a rise time of 4 ns. There is no breakdown at <inline-formula> <tex-math notation="LaTeX">$U_{p} < 27$ </tex-math></inline-formula> kV, and at <inline-formula> <tex-math notation="LaTeX">$U_{p} > 27$ </tex-math></inline-formula> kV, a pseudospark discharge starts, which transforms at <inline-formula> <tex-math notation="LaTeX">$U_{p} > 45$ </tex-math></inline-formula> kV into a surface discharge. The working gas is dry air at a constant pressure of 13 Pa. Using these parameters, electric field simulations of the triple point junctions are conducted and time-integrated pictures of the different discharge modes are presented. When the gas pressure is increased from 13 to 35 Pa, the voltage range of the pseudospark discharge mode grows from 13 to 65 kV.