GB457253A - Improvements in electric discharge tubes - Google Patents

Abstract

457,253. Discharge apparatus. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, Emmasingel, Eindhoven, Holland. April 6, 1936, No. 10113. Convention date, June 27, 1935. [Class 39 (i)] In an electric discharge tube comprising a plurality of electrodes which are at different potentials, the potential of at least one electrode is derived from a potentiometer located within the tube and comprising a layer of conductive or semi-conductive material on an insulating electrode support. Fig. 2 shows a cathode ray tube in which a tubular ceramic member 9 encloses and supports the electrodes which are, in order, an indirectly-heated cathode 1, Wehnelt electrode 3, disc 4, cylinders 5, 6 and deflecting plates 7, 8. The electrodes 4, 5, 6, form an electron lens system and are maintained at increasing positive potentials from the cathode. The application of the potentiometer to this tube is shown in Fig. 1. Four metal bands 17 surround the insulator 9 and are connected to cathode 1, and electrodes 4, 5, 6. Connecting leads pass only to electrodes 1 and 6, the potentials of 4, 5 being derived from conductive coatings 18, 19 forming a potentiometer. Before insertion in the tube the insulator 9 is given a graphite coating in the region of the potentiometer layer. After evacuation the layers 18, 19 are deposited by evaporation of magnesium from two sources heated by separate heaters, high-frequency induction, or electron bombardment.. The resistances of the two layers are adjusted independently until the correct potentials are obtained. The layers may also act as getters.