ARMY FOREIGN SCIENCE AND TECHNOLOGY CENTER CHARLOTTESVILLE VA
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A thermionic cathode was prepared by deposition of a high temperature emissive metal, such as Th on a matrix of a refractory metal, such as W. To lower the activation temperature and to shorten the time required for activation of the cathode, the emissive metal was deposited on the cathode core from the gas phase produced by thermal dissociation of a halide of the emissive metal while passing a heater current through the electrode core. Simultaneously, a metal increasing the atom mobility of the emissive metal such as Zr was deposited from its halide in the gas phase. Then, the matrix metal was deposited from its halide below the dissociation temperature of the halide, but over the sublimation temperature of the halide of the emissive metal, and when a stable heater current was obtained, the matrix metal was deposited at the dissociation temperature of its halide.
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