GB447536A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

447,536. Discharge apparatus. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. Aug. 14, 1934, No. 23448. Convention date, Aug. 16, 1933. [Class 39 (i)] A device contains, in addition to the main electrodes, an auxiliary cathode adapted to generate positive ions independently of the main discharge, and the gas-pressure is so high that the cathode drop is approximately equal to the ionization potential, the auxiliary cathode being so arranged that the independent discharge further reduces the cathode drop. In one form, in a rectifier a discharge is maintained between a thermionic or cold cathode and an anode across the path of the main discharge, the voltage drop of which is thus reduced. The gas-pressure is equal to or greater than 1 micron, for example, 3 microns. The cathode may be alkaline-, earth-, thorium- or caesium-coated. In a modification, an auxiliary cathode 24, Fig. 3, negatively biassed with respect to the main cathode 20, is arranged inside the anode 28, and the auxiliary discharge is varied by a transformer 46. The auxiliary cathode may be housed in a cylinder having a constricted aperture adjacent the main cathode. In another modification, the auxiliary cathode is arranged inside the main cathode which consists of a double-walled cylinder having heaters between its walls. The anode is then constituted by two plates closing the ends of the cathode. In a lamp, Fig. 6, the auxiliary cathode 69 is arranged inside the main cathode 63, which is heated by a filament 67 and is surrounded by heat shields. The auxiliary cathode may surround the main cathode and may be unheated if it receives emissive material sputtered from the main cathode. Specification 298,906, [Class 39 (i)], is referred to. Reference has been directed by the Comptroller to Specifications 363,914, 393,849 and 396,725.