Comparison of velvet- and cesium iodide-coated carbon fiber cathodes

Presents results of an experimental comparison of a velvet cathode- and a carbon fiber cathode-coated with cesium iodide (CsI) salt. Each cathode had a planar geometry, with similar emission areas. The cathodes were tested at electric field strengths of 50 kV/cm at anode-cathode (A-K) gaps of 4.0 cm. The applied voltage had a 1-/spl mu/s duration and the pulser was operated at up to a 1-Hz repetition rate. The system had a low base pressure (<1.0/spl times/10/sup -7/ torr). This paper reports the results and comparisons of experiments on each cathode. We address the current and voltage characteristics, the shot-to-shot reproducibility, the pressure evolution of the diode under 1-Hz operation, and the lifetime of the cathodes.