Electron beam generation by an electron cyclotron resonance plasma

Electron guns based on a plasma, instead of a thermionic material cathode, are gaining more attention due to their ability to generate beams of a variety of sizes for both pulsed and steady state operation. These guns have a major advantage in that they have no material cathode, can drive current densities larger than their thermionic counterparts, and can operate reliably at relatively high pressures (for example, fore vacuum gas pressures). This paper presents initial results on the characterization of a plasma cathode electron source driven by a microwave electron cyclotron resonance plasma discharge. A negatively biased plasma chamber is electrically isolated from the downstream system, and electrons from the discharge are extracted through a small aperture. These electrons then interact with background gas in the main chamber. Electron beams of greater than 80 A have been calculated based on measurements in this configuration.