GB227858A - Improvements relating to vacuum electric discharge devices - Google Patents

Abstract

227,858. Westinghouse Electric & Manufacturing Co., (Assignees of O'Brien, B.). Jan. 16, 1924, '[Convention date]. Void [Published under Sect. 91 of the Act]. Low - pressure metallicvapour apparatus; vacuum tubes.-A discharge tube in which the current is carried by a stream of electrons emitted from a cathode is provided with means whereby the anode is caused to emit positive ions. For this purpose a substance such as caesium may be inserted in an exhausted bulb, and the anode heated to a temperature at which caesium atoms striking it are evaporated as positively-charged caesium ions; the adsorbed film of caesium produced on the cathode also improves the electron emissivity. The arrangement enables lower voltages to be used between the electrodes. Tungsten is a suitable metal for the electrodes. As shown, a cylindrical cathode 21 is mounted around a control electrode 19, preferably of tungsten, and an anode consisting of a metallic core 16 with a winding 17 and a cylindrical cover 18. The bulb is exhausted and is in communication with a side tube 9 containing caesium 11. The anode is heated inductively by the winding to a temperature above the critical temperature at which the Richardson work function exceeds the ionizing potential of caesium. The cathode is heated by radiation from the anode. In another arrangement une cathode and anode consist of filaments, and the anode is heated to a higher temperature than the cathode which is only slightly heated.