GB820736A - Method of and apparatus for electron multiplication - Google Patents

Abstract

820,736. Discharge apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Feb. 4, 1957 [Feb. 11, 1956], No. 4366/56. Class 39(1). A method of electron multiplication in which an output current, variable at all times with a variable input current, is obtained, comprises causing an electron stream to pass in succession through a series of electrodes in a gas, using the Townsend electron avalanche process in the gas at the stages between the electrodes, and attenuating at the interposed electrodes the effects which may cause feedback between any two stages. In the electron multiplier shown a cathode 10 and an anode or collector plate 14 are located at the ends of an assembly of apertured electrodes 11 mounted on conductive rings 12, e.g. of brass, spaced by insulating rings 13, e.g. of ceramic. A thin window 11A permits high energy particles or incident light to impact the cathode. Alternatively electrons may be emitted from the cathode by a nuclear reaction therein, or may be released by ionization of the gas, or may be introduced into the input region by any other means. The anode 14 has an inlet 15 for the gas filling, which may be air at a pressure of from 1/10 to ¢ mm. of mercury. An outlet may be provided to permit the gas to circulate, or the inlet may be sealed after filling. The rings 12 are adapted for connection to a potential divider. A grid may be placed between the anode 14 and the last electrode 11 and held at a fixed potential, and the time constant of the anode circuit may be made small by connecting a condenser in series with a restrictive load to enable very short pulses to be amplified. The apertures in the electrodes 11 may be formed by punching holes or by a photoengraving process. The holes are staggered in position in successive electrodes and may be confined to a central circular area of the electrodes. An axial magnetic field may be applied. In an alternative arrangement, Fig. 3 (not shown), the apertured electrodes are in the form of wire grids and the electrode assembly is enclosed in a vacuum tight envelope of insulating material, the cathode being connected to a negative voltage and a lead from the grid next adjacent the anode being connected to earth through a resistor. The rings 13 are made of resistive or semi-conductive material to provide uniform potential drops between the grids. The anode is insulated from the adjacent grid and has a lead for the output current.