Oxygen-supported beryllium-cathode for crossed-field amplifiers

Several years ago, beryllium was selected as the secondary emission cathode material in a medium power S-band crossed-field amplifier (CFA). The CFA operated with 125KW peak output and 12 db gain. Tungsten dispenser cathodes had exhibited short life; beryllium was selected because its oxide surface was believed stable and capable of good secondary yield at low primary energy levels. It too exhibited short life, presumably because of either contamination or depletion of its oxide surface. The incorporation of an oxygen dispenser to provide a low background (10^-6to 10^-7Torr) of oxygen and a small Vac-Ion^®pump to stabilize internal pressure has produced a reliable berylliun cathode system.