Electron Emission from Pseudospark Cathodes

摘要

The pseudospark cathode has the remarkable property of macroscopicallyhomogeneous electron emission at very high current density (>1 kA/sq cm) over a large area (several sq cm). The model of electron emission presented here is based on the assumption that the pseudospark microscopically utilizes explosive arc processes, as distinct from earlier models of anomalous emission in superdense glow discharges. Explosive emission similar to vacuum are cathode spots occurs rapidly when the field strength is sufficiently high. The plasma remains macroscopically homogeneous since the virtual plasma anode adapts to the cathode morphology so that the current is carried by a large number of homogeneously distributed cathode spots which are similar to type 1 and type 2 spots of vacuum arc discharges. The net cathode erosion is greatly reduced relative to spark gap-type emission. At very high current levels, a transition to highly erosive spot types occurs, and this arcing leads to a significant reduction in device lifetime. Assuming vacuum arc like cathode spots, the observed current density and time constants can be easily explained. The observed cathode erosion rate and pattern, recent fast camera data, laser induced fluorescence, and spectroscopic measurements support this approach. A new hypothesis is presented explaining current quenching at relatively low currents. From the point of view of electron emission, the superdense glow or superemissive phase of pseudosparks represents an arc and not a glow discharge even if no filamentation or arcing is observed.