Optimization of a low-pressure hollow-anode electrical discharge for generation of high-current electron beams

We report results on the optimization of the design of a high-current hollow-anode (HA) electrical discharge electron beam source that is triggered by a ferroelectric surface discharge. For the ferroelectric sample, we used a BaTi solid solution with a large dielectric constant (epsilon approximate to 1600). Three different electric schemes for ignition and sustainment of the HA discharge were investigated. The studied HA designs allow reliable ignition and sustainment of the discharge with current amplitude of up to 1.2 kA and pulse duration of up to 2 x 10(-5) s, with and without gas flooding. It was found that the rise time of the discharge current monotonically decreases from similar to 10-7.5 mus with the increase of the background pressure from 4 x 10(-5) to 7 x 10(-5) Torr. Generation of high-current electron beams was demonstrated under an accelerating voltage of up to 300 kV and similar to400 ns pulse duration. It was shown that the use of an optimal resistor which supplies an auto-bias potential to the HA output grid eliminates almost entirely the plasma pre-filling of the accelerating gap prior to the application of the accelerating pulse. In addition, it was found that within a certain range of time delays (12.5-15.5 mus) of the application of the accelerating pulse with respect to the beginning of the HA discharge, the amplitude of the diode current remains practically unchanged in spite of a considerable decrease in the amplitude of the discharge current.