Current-Limiting Mechanisms in Gas Discharge Excited with Pulsed Voltage with Nanosecond Fronts

The characteristics of barrier gas discharge in helium at atmospheric pressure are investigated for a pulsed voltage with a voltage rise edge of 2.5–10 ns and a pulse repetition rate of 5–100 kHz. In the homogeneous discharge mode, a pulse current is up to 80 A with a peak power up to 1.5 MW and a specific power up to 250 W/cm3. Increasing the steepness of excitation pulses slightly affects the discharge current magnitude, but allows maintaining the volumetric mode of current distribution for higher operating voltages. It is shown that the discharge current is enhanced by emitted electrons when the ionization front approaches the cathode sheath and limited by the charge accumulation on the dielectric layer on the cathode. As a result of the charge accumulation and the dielectric floating potential increases the potential drop on the cathode sheath diminishes. An increase of the gap between electrodes and the voltage causes the transition between homogeneous to contraction modes of the current flow.