Influence of Electrode Geometry and Gas on the Breakdown Voltage of Hollow Cathode Discharge With Spark Geometry Under Nanosecond Pulses

Pseudospark-sourced electron beam with high energy can be produced by the pseudospark device. In this paper, the breakdown voltages of the hollow cathode discharge with the pseudospark geometry influenced by electrode geometry and the gas have been studied and analyzed. In the wide range of pressure and gap, the breakdown voltage increases with the increase in the pressure and the gap distance. There is a pressure threshold and a gap distance threshold, below which the discharge mode will change. The product of the pressure threshold and the gap distance threshold is about 65 Pa · mm. The breakdown voltage is affected by the aperture diameter and the gap distance together. When the ratio of the gap distance to the aperture diameter is greater than 4, the electric field inside the small hole is almost zero and the discharge is converted to the plate electrode discharge. When the ratio is in the range of 0.67-4, the breakdown voltage decreases with the increase in the aperture diameter. When the ratio is less than 0.67, the breakdown voltage hardly changes with the aperture diameter.

I. Introduction

Pseudospark discharge has attracted considerable attention due to its potential applications in such diverse areas as high-power switching, electron beam lithography, plasma processing, free electron lasers, and high-brightness electron beam sources for advanced accelerators [1]–[6]. The pseudospark discharge under both pulsed voltages and dc voltages can generate high-brightness intense electron beams, with high electron energies, currents in a wide range, power densities up to 10⁹ W/cm−2, and small diameters of 0.2 mm [3], [7]–[9]. The pulsed electron beam is now developing as a useful tool for surface modification of materials [10]. From the 1980s, many studies have been carried out. Schoelch [11] has prepared high-temperature superconductive film yttrium barium copper oxide with pulsed electron beams ablation. Liu et al. [12] have prepared the nanometer films with pseudospark electron beam deposition.