GB515097A - Electron multiplier - Google Patents

Abstract

.515,097. Electron multipliers. FARNSWORTH TELEVISION, Inc. May 23, 1938, No. 15283. Convention date, June 5, 1937. [Class 39 (i)] In a multiplier, the secondary electrons are subjected to a field to deflect the ions out of the electron path. A multiplier comprises an indirectly- or directly-heated cathode 5, Fig. 1, space charge grid 6, control grid 7, and secondary-electron-emitting members each in the form of an annular cup 9 having one wall joined by a metal ring 11 and a ring 10 of knitted fabric. A final plateshaped secondary emitter 25 and a collecting mesh 21, supported by rings 24, are also provided. Signals are fed to the control grid through a condenser 26. The electrostatic field existing between the electrodes causes the electrons to flow in the path indicated by the light arrows, and the ions in the paths indicated by heavy arrows -to fall on surfaces which are not sensitized to emit secondary electrons. By using resistances 35 and potentials which will given an increased secondary emission, the device may be made regenerative. Similarly, the devicemay be used for reverse feed back if the secondary-electron emission is small. For use as a modulator, radio-frequency potentials are applied to the grid 6 through 40, Fig. 2, and the modulating signal to the secondary electrode 9 which is connected to 'the source 29 of direct potential through an impedance 35. If the condenser 41 is omitted, both the radio-frequency and the modulating signal may be applied to the grid. In another form, the carrier and signal frequencies may be applied to separate grids. The output circuit 42 is connected to the collecting electrode 25. In a further form, photo-electrons from an image dissector are projected through a scanning aperture on to a conical secondary emitter. In other forms, curved surfaces 60, Fig. 4, are used, only those parts on which the secondary electrons are projected being sensitized, and a collecting anode 65 is provided. Fig. 5 shows another construction of secondaryemitting electrode 67 adapted to produce linear operation. Specification 482,026 and 494,351 are referred to.