GB420497A - Improvements in and relating to gaseous electric discharge devices - Google Patents

Abstract

420,497. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. July 9, 1934, No. 20123. Convention date, July 13, 1933. [Class 39 (i)] A gas-filled device comprises a tubular envelope with an anode near one end and a high resistance cathode extending the length of the envelope, the cathode current lead being connected to the cathode at the end remote from the anode and the cathode resistance being such that when the cathode is covered with a uniform glow the potential gradient along it is the same as that in the surrounding gas column. In one form, Fig. 1, the anode is a short nickel wire 4 whilst the cathode consists of a fine wire 6 wound helically round a glass tube 5 and having its end taken out from the top inside the tube 5. The resistance of the wire 6 is of the order of 250 to 5000 ohms per inch, and the material may be iron, tungsten or the substance known under the Registered Trade Mark "Nichrome." The top of the tube 5 may be closed by a bead of glass. The wire 6 may be covered with a mixture of barium azide and ¢ per cent of caesium azide. In a modification the cathode inlead passes through the tube 5 and supports a rod of high resistance material, such as a coated glass rod, running the length of the tube. In another modification an auxiliary cathode consisting of a short rod adjacent the anode may be inserted, and a permanent discharge maintained between it and the anode. The filling may comprise neon, helium, argon, or mercury vapour, or neon containing 0À4 per cent of argon at a pressure of between 10 mms. and 40 mms., for example 20 mms. The tube may be used as a visual ammeter. Specification 411,669 is referred to.