Characterization and Switching Performance of Electron-Beam Controlled Discharges

The electron-beam sustained discharge switch is an attractive concept for repetitive pulsed power switching because it has a demonstrated capability to interrupt direct current and because it is inherently scalable. We report on experiments with this type of switch in a 4-kV dc circuit. A wire-ion-plasma (WIP) electron-beam (e-beam) gun is used to irradiate and sustain a switch discharge with a 100-cm2 cross-sectional area in 1 atm of N2 or CH4. Interruption of 8-10-μs pulses of up to 1.9 kA, and of 100-μs pulses of 150 A has been demonstrated in methane, and interruption against higher recovery voltages (11 kV) has been performed at 1.2 kA by adding series inductance to the circuit. These values represent power supply limitations rather than limitations of the switch itself. A comparison of the measured discharge characteristics with theoretical predictions shows that the measured switch conductivities are higher than the predicted values for given e-beam current values. A qualitative explanation for this observation is offered by considering the effects of electron reflection from the discharge anode and of nonlinear paths for the beam electrons across the discharge gap. We conclude that the switching performance of the e-beam controlled discharge switch corresponds to its design parameters, and that for a given switch size a lower voltage drop during the on time can be expected compared with the voltage drop predicted by previously published theory.