GB485620A - Improvements in electron multipliers - Google Patents

Abstract

485,620. Electron multipliers ; circuits. FARNSWORTH TELEVISION, Inc. Nov. 18, 1936, No. 31646. Convention date, Jan. 27. [Classes 39 (i) and 40 (v)] An electron multiplier comprises a secondary emitting cathode 1, Fig. 1, surrounding an anode 10 ; when a resonant circuit of suitable frequency is connected between the anode and cathode oscillations are set up, the electrons passing through the anode between successive impacts on various portions of the cathode surface. If the device is not self-starting an electron gun comprising a cathode 14, modulating electrode 16 and anode 20 may be used to direct a modulated stream of electrons into the space within the cathode ; the device will then act as an amplifier. As shown in Fig. 5 two such tubes may be connected in push-pull as a balanced modulator, the grids 16 being supplied in opposite phase from the oscillator 40, and in the same phase through coupling condenser 39. The frequency of the resonant circuit is chosen so that the time of flight of an electron across the tube is one or more complete periods of the oscillation. The cathode is of copper coated with aluminium, nickel, caesium or caesium oxide and may be mounted within the tube or may form part of the envelope when a watercooling jacket 42 may be added. Part of the cathode may be made photo-electric to enable primary electrons to be generated by a modulated light beam. Specifications 450,138 and 451,724 are referred to. The Specification as open to inspection under Sect. 91 describes also a form in which the time of flight of the electrons is much shorter than the period of the oscillations generated. This subject-matter does not appear in the Specification as accepted.