This paper presents the results of experimental investigations on the generation of supershort avalanche electron beams (SAEB) at nanosecond discharges initiated in gas-filled diodes. In air, at a pressure of 1 atm with a sharply non-uniform electric field, an SAEB is generated from the inter-electrode gap at a solid angle exceeding 2π sr. Reduction of gap d between the cathode and the anode leads to a decrease in the current amplitude of the beam incident on the lateral walls of the gas-filled diode and in an increase in the pulse duration of the beam current both in the axial and radial directions. Pulses of the beam current initiated on the lateral surface of a tube cathode have been recorded. It is shown that to generate electrons with an ‘anomalous’ energy, cathodes with an increased radius of curvature should be used.

The breakdown of different air gaps at high overvoltages in an inhomogeneous electric field was investigated with a time resolution of up to 100 ps. Dynamic displacement current was used for diagnostics of ionization processes between the ionization wave front and a plane anode. It is demonstrated that during the generation of a supershort avalanche electron beam (SAEB) with amplitudes of ∼10 A and more, conductivity in the air gaps 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. The amplitude of the dynamic displacement current measured by a current shunt is 100 times greater than the SAEB. It is shown that with small gaps and with a large cathode diameter, the amplitude of the dynamic displacement current during a subnanosecond rise time of applied pulse voltage can be higher than 4 kA.

This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be ∼25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach ∼25 ps too.

The results of experimental studies of the parameters (amplitude and duration) of a supershort avalanche electron beam (SAEB) generated in air at atmospheric pressure are presented. It is shown that...