High quality pseudospark electron beams for millimetre-wave sources

Experimental studies of the production and propagation of an electron beam from a multi-gap pseudospark discharge chamber are presented. A beam up to 680 A was measured at the anode when a three-gap pseudospark underwent a breakdown at an applied DC voltage of 23 kV. This beam can propagate further downstream as far as 20 cm in length in a gaseous environment (pressure = 60 mtorr) with no guiding magnetic field. The recorded beam traces at two different positions along the drift tube and the cross-section image of the electron beam further confirm that the transport of the electron beam was based on the neutralization of the space-charge of the electron beam due to the ionization of the gas molecules by the beam itself. The beam produced is of very small size of 1-3 mm in diameter and is ideal to drive high frequency radiation due to its small beam size and the compactness of the device. Therefore higher energy electron beam pulses were further generated from a 14-gap pseudospark discharges powered by a pulsed power system (a cable pulser) capable of producing 120 ns duration and 170 kV voltage pulses. The beam produced is of very small size of 1-3 mm in diameter and is measured with current up to 110 A. Interactions between the electron beam and a Ka-band and W-band slow wave structure were simulated and designed. The beam-wave interaction experiments were conducted and microwave pulses were detected successfully from the 14-gap pseudospark-based electron beam-wave interaction experiments.