Effect of accelerated electrons on the glow structure of nanosecond diffuse discharge in the rod–plane air gap

A diffuse discharge in a rod (cathode)–plane gap with an interelectrode spacing of 10 cm is studied in air at atmospheric pressure. The cathode voltage is 370–390 kV at a pulse FWHM of about 70 ns. It is shown that a pulse-to-pulse variation in delay time of the discharge formation in an interval of 3–15 ns leads to variations in the discharge current and X-ray pulse amplitude in intervals of 100–200 A and 20–250 relative units, respectively. A relationship of the amplitude of the X-ray pulse and structural parameters of the discharge glow is obtained. It is shown that fast electrons with energies of less 30 keV that are accelerated by strong electric field in the vicinity of the cathode play the key role in the formation of the longitudinal structure of glow at relatively large delay times of the discharge formation. Fast electrons ionize peripheral regions of the discharge, increase its cross section, and, hence, provide a decrease in the current density, specific energy deposition, and radiation intensity at a distance from the cathode that corresponds to electron path in air.