GB523281A - Electron discharge devices - Google Patents

Abstract

523,281. Electron-multipliers. STANDARD TELEPHONES & CABLES, Ltd. Dec. 30, 1938, No. 37851. Convention date, Dec. 31, 1937. [Class 39 (i)] The cathode 20, preferably in the form of a thin walled hollow cylinder of silver with a silver-caseium oxide surface, is surrounded by the anode 30 which comprises a squirrel-cage or other openwork cylinder of a non-magnetic material such as copper or aluminium. An axial magnetic field is produced by solenoids 41, 42, or by a permanent magnet which is preferably housed in a re-entrant part of the envelope which extends downward inside the cathode, and in which the latter is supported by mica washers. When the device is used as an amplifying photo-electric device, the anode and cathode are connected across a source of high frequency potential 61, a steady biassing potential 50, and an output resistance. The photo electrons excited by the source 100, are sent back to the cathode in looped paths, and, as long as the cathode is becoming more positive, strike it with sufficient energy to release secondary electrons, which then follow a similar path. Electron multiplication continues until the potential imposed on the cathode begins to fall ; all the electrons then move outwards to the anode. For operation as an oscillator the device is connected as shown in Fig. 7 to a tuned circuit 81, which is coupled to the output circuit. Oscillations may be initiated by opening and closing the circuit and may be modulated by incident light. Alternatively the anode may be opaque and the cathode non-photo-electric, so that the device operates simply as a multiplier. The device may be mounted in a parabolic reflector to concentrate light on the cathode.