Photofield emission from tip cathodes

Summary form only given, as follows. We are studying photofield emission from tip cathodes. In photofield emission a cathode is biased to high fields and then irradiated with light. In principle, for fields at the cathode of the order of 0.1 V/Angstrom and greater, the effective work function of the cathode is lowered and the quantum efficiency of photoelectron production increases. In our experiments a cathode of tip radius /spl sim/1 micron is biased by applying a pulsed voltage up to 50 kV and pulse duration of up to 200 ns. During the voltage pulse a 25 ns excimer laser pulse is incident on the cathode tip. Typically we have been using XeCl in the excimer which generates a wavelength of 308 nm. In experiments using a tungsten (work function of /spl sim/4.5 eV) tip we have generated more than 250 mA in a pulse using the /spl sim/3 eV excimer light. Our current experiments on LaB/sub 6/ cathodes and field emitter arrays will be discussed.