Discharge Current and Current of Supershort Avalanche E-Beam at Volume Nanosecond Discharge in Non-Uniform Electric Field

Summary form only given. In recent years more interest is being shown in nanosecond discharges in high-pressure gases, formed in non-uniform electric field. Previously, a cathode with small- curvature radius was used, and the gap was applied with high voltage pulses with amplitude up to 400 kV. In these conditions the runaway electrons and (or) X-ray radiation are registered, and the discharge plasma may be used as a source of spontaneous and laser radiation, and as a source of X-ray radiation with high pulse repetition rate up to 3 kHz. However, the volt-ampere characteristics of nanosecond discharges were less studied mainly due to difficult recording the discharge current pulses with subnanosecond resolution. This work was to investigate the character of discharge current flowing in a gas diode, used for supershort avalanche e-beam generation (SAEB), and to determine the time of SAEB generation with respect to the discharge current pulse. A discharge of atmospheric pressure air in a non-uniform electric field has been investigated. Formation time of a supershort avalanche electron beam with respect to the discharge current pulse was defined. It has been shown that SAEB is recorded in a volume discharge at the current pulse front, and the SAEB maximum current is achieved before the first peak of current at the discharge current front, that is determined by the gas diode capacitance discharging through plasma. At that, with the use of RADAN-220 generator, and an insulator made of a standard vacuum X-ray tube IMA- 350D, SAEB appearance advances the first peak by ~100 ps. The recorded amplitudes of the bias currents were above 1 kA. The mentioned bias currents appeared due to charging of the capacitor, which was formed by the dense plasma with its front expanding from the cathode and the fiat metallic anode.