GB566542A - Improvements in high frequency electronic discharge devices - Google Patents

Abstract

566,542. Glass manufacture. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). July 19, 1943, No. 11731. [Class 56] [Also in Groups II, XXXVI and XL] A tetrode suitable for incorporation in a resonator system in a similar manner to the triode described in Specification 554,154, [Group XL], comprises four plates 1, 2, 3, 4 sealed together by glass tubes 5, 6, 7, the outer plates 1, 4 forming the end of the valve and carrying the cathode 10 and anode 16 respectively, and the inner plates 2, 3 carrying grids 8, 8<1>. The cathode comprises a plate of molybdenum 10 coated with thorium oxide and heated by electron bombardment from a filament 12, and supported by wires 11 or a thin metal foil from the tube 9 which joins the cathode to the plate 1. A focusing shield 15 surrounds the filament.and the leads to the filament pass out through seal 14. The grids 8, 8<1> are brought into close proximity by conical portions 21, 22 which enable the plates 2, 3 to be kept at a safe distance. Anode 16 has a hole 18 communicating with an exhaust tube 19. A screw 17 engages a corresponding nut on a resonator wall. The plates 1-4 may be of an alloy of 54 per cent iron, 31 per cent nickel and 15 per cent iron, 31 per cent nickel and 15 per cent cobalt which seals easily to glass, or low carbon steel used in conjunction with an iron-matching glass described in Specification 536,362. To increase the conductivity, the plates may be coated with a layer of copper 1-4 mils thick ; if the nickel-cobalt-iron alloy is used, it will then be necessary to apply a fluxing glass of composition SiO2 56 per cent, B2O3 10 per cent, Al2O3 3 per cent, PbO 28 per cent and K2O 3 per cent between the plates and the glass tubes.