Verfahren zur Herstellung von Vorratskathoden

756,767. Thermionic cathode constructions. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. April 2, 1954 [April 2, 1953], No. 9805/54. Class 39 (1). A plurality of identical metal tubes 1 the lengths of which are at least equal to their diameters are arranged contiguously with their ends in one plane, and the tubes are filled with electron-emitting oxide so that the ends form a plane emissive surface. As shown, nickel tubes of 0.01 mm. in wall thickness and 0.5 mm. upwards in height may be ordered by a magnetic sorter, Fig. 4 (not shown), and secured within a box 2 of nickel or molybdenum by simple heating to 1050‹ C., by nickel powder paste applied to base 4, or by brazing with copper, platinumsilver or copper-nickel alloy. The heater 5 is assembled behind the base 4. After filling with alkaline-earth carbonates with, if desired, a top layer overall of depth 10Á, the material is activated at 1100‹ C. falling to 850-900‹ C. Nickel powder may be added to the emissive material. A store of emissive material may be interposed between the base 4 and the lower ends of the tubes, the spaces between the tubes 1 being filled by wires 9, Fig. 6a, to improve capillary action in use. In a modification a honeycomb structure 1, Fig. 7, is made by mounting a number of nickel-coated aluminium wires within a nickel tube 2, swaging the tube to press the wires together, cutting into sections, and dissolving out the aluminium with caustic soda; or tantalum-coated nickel or iron wires may be treated with hydrochloric acid. The emissive material may be thoria activated at 1600-1800‹ C. and a reserve 7, Fig. 9, may be left between the base 4 and the honeycomb structure 1. Two cylindrical heat shields of tantalum or copper may surround the whole cathode.