Low Work Function Collectors.

摘要

Films of Cs-Sb, Cs-Al2O3-Al, Cs-Ta2O5, Cs-WC, Cs-Au, Cs-Bi, Cs-Pb, and Cs-Ni-Sb were studied as collector electrodes. Relative collector work functions were compared in a multiple collector device using cesium reservoir temperatures as high as 300 C, current densities up to 10 amps/ sq.cm, and ratios of collector-to-cesium-reservoir temperature up to 1.35. The Cs-Sb collector was found to have a minimum thermionic work function of 3.3 - 1.4 eV at a temperature ratio of 1.3 1.5. At lower temperatures the oxide collectors had lower work functions than Cs-Sb, but none of these collectors was at its minimum work function. The resistance of the 30-Angstrom thick Al2O3 was too large for practical application. When a Cs-Sb on W electrode was used as an emitter above 1000 K, sublimation of Sb from Cs-Sb was sufficient to quench the ignited plasma mode. Alloying Sb with Ni drastically reduced sublimation of Sb in vacuum and in cesium vapor without significantly changing the thermionic work function. The ignited mode was observed with the NiSb2 emitter. The semiconductor-dispensing emitter did not display emitter characteristics any better than those available with present emitters. (Author)