GB207800A - Improvements in and relating to electron discharge devices - Google Patents

Abstract

207,800. British Thomson - - Houston Co., Ltd., (Assignees of Mackay, G. M. J., and Charlton, E. E.). Nov. 29, 1922, [Convention date]. Low - pressure metallicvapour apparatus.-A rectifier or other tube containing an incandescent cathode and one or more other electrodes is highly exhausted and supplied with caesium or rubidium vapour which is maintained at a temperature such that the vapour pressure is about 0.02 mm. of mercury', so as to increase materially the electron emissivity of the cathode. The cathode 2 consists of molybdenum or nickel, or of tungsten with or without a small addition of thoria, and is surrounded by an anode 3 of molybdenum, nickel, or tungsten. A tube provided with two bulbs is sealed to the container 1 and the whole baked at 450‹ C. and exhausted. A mixture of caesium chloride and calcium is introduced into the tube which is then closed. The container and tube are again heated and exhausted, care being taken to remove all moisture. Caesium is reduced by heat and distilled into the bulbs, and passes thence into the container, the tube being then sealed off. In operation the secondary 15 of a transformer and a load such as a battery 16 are connected between the cathode and anode, and the cathode may be heated from a tapping across the secondary. The heating circuit may be opened by means of a switch 19 if sufficient heating of the cathode is produced by bombardment by positive ions. The device should be worked at a temperature of 150‹ C. but in some cases a preliminary operation at 200‹ C. may be necessary. The container may be surrounded by a heat-retaining jackest or by a heater 18. Double-wave rectification may be obtained by the use of two cylindrical anodes of the same diameter surrounding a single cathode. The space current may be increased by providing a winding around the container setting up a magnetic field. The cathode may consist of a tube heated internally by a resistance. Specifications 184,446 and 201,893 are referred to.