Characterization of a Heaterless Hollow Cathode

The parameters of a thermionic heaterless hollow cathode operating in the diode mode were determined using various diagnostic methods, and studied in relation to the discharge current, in the range 0.5-1.5 A, the orifice plate anode gap, and the xenon-gas flow rate. It was shown that the cathode ignition consists of breakdown, heating, and keeping phases, and it realizes in the timescale of a few seconds depending on the xenon-gas flow rate. Dependencies of the cathode and orifice potential vs the gas flow rate and discharge current were obtained. The plasma plume parameters (plasma density and temperature) were studied using double Langmuir probe and spatial resolved optical spectroscopy. The energy distribution of the generated electron beam was obtained by the retarding energy analyzer and biased collimated Faraday cup. The processes involved in the hollow cathode ignition, heating, and dc operation are discussed, and the influence of initial conditions on the reliability and efficiency of the operation of a hollow cathode is determined. Finally, a simple model for estimation of the emitter temperature during the cathode operation is suggested.