GB853177A - Amplifier circuit embodying a gas or vapour filled discharge tube - Google Patents

Abstract

853,177. Discharge tubes. SOC. D'ELECTRONIQUE ET D'AUTOMATISME. Dec. 2, 1957 [Nov. 3, 1956], No. 37508/57. Class 39(1). An amplifier circuit includes a gas or vapour filled discharge tube comprises at least a cathode, an anode and a control electrode within a single envelope in which is provided a beta-particle emitter to produce a permanent ionization of the gas or vapour atmosphere so that only a small potential difference is needed across the cathode and anode of the tube to maintain a discharge. The tube shown comprises an anode 2, control grid 3 and a thin (e.g. 25 microns) hollow nickel cylinder 5 carrying on its outer surface an emissive layer 4 of carbonates and/or nitrates and/or oxides of a good electron emitting element such as barium or strontium, and on its inner surface a thin layer or film 6 of a radio-isotope such as silicon 31, thallium 204 or carbon 14, which emits beta-particles. The nickel cylinder 5 protects the isotope from impact by ions in the discharge and a beta-particle shield may be inserted between the isotope and the envelope of the tube. With a filling of helium or neon the potential difference applied between the anode and cathode by a battery 7 may be lower than 24 volts ; with hydrogen, nitrogen, argon, klyston or xenon, lower than 12 volts, and with a metallic vapour such as mercury or cadmium, lower than 6 volts. In an alternative arrangement the radio-isotope is deposited on thin rods arranged evenly around the cathode and preferably within the cathode dark space, each film of isotope being protected from impact by ions by a thin nickel cylinder. A thermionic cathode may be used, with part at least of the beta-particle emitter material carried by the heater filament. The control grid 3 is negatively biased by a battery 10, an input signal is applied across the terminals 12 of an impedance 11, and an amplified signal is obtained at the terminals 9 of an impedance 8.