Dynamic displacement current in subnanosecond breakdowns in an inhomogeneous electric field

The aim of the work was to take measurements during subnanosecond breakdowns with a time resolution no worse than 100 ps. The current through gaps filled with atmospheric pressure air was investigated during the generation of runaway electrons and X-rays. Three generators, when ensuring the formation of a runaway electrons preionized diffuse discharge (REP DD), were used. It is confirmed that during a subnanosecond voltage rise time, the amplitude of the dynamic displacement current can be higher than 4 kA. It is demonstrated that during the generation of supershort avalanches electron beams with amplitudes of 10 A and more. The conductivity in the air gap at the breakdown stage is ensured by the ionization wave, whose front propagates from the electrode of small curvature radius, and by the dynamic displacement current between the ionization wave front and the plane electrode.