Analysis of the Anomalous High-Current Cathode Emission in Pseudospark and Back-of-the-Cathode Lighted Thyratron Switches.

摘要

An analysis of the anomalously large cathode emission recently observed in the superdense glow of pseudospark and back-lighted thyratrons is presented. These switches are low-pressure (27 PaH2) glow-discharge pulsed-power devices. After operating at peak discharge currents of 6-8 kA and pulse durations of 0.5-1 microsec., the surface surrounding the cathode hole was found to have been homogeneously melted within a radius of approx. 4 mm indicating that the discharge is a superdense glow discharge, not an arc, with a cross-sectional area on the order of 1 sq cm. This conclusion is also supported by streak camera measurements. The current density at the cathode surface under these conditions is 5-10 kA/sq cm, several orders of magnitude larger than that of thermionic cathodes in common thyratrons. This high-current density is explained by intense cathode heating from a high-current density ion 'beam' produced in the cathode fall during the initial stage of current buildup. The surface heating resulting from this 'beam' yields a significant field-enhanced thermionic emission of electrons. Reprints. (RRH)