GB404299A - Improvements in and relating to electron discharge devices - Google Patents

Abstract

404,299. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. Crown House, Aldwych, London.-(Assignees of Coolidge, W. D. ; 1480, Lenox Road, Schenectady, New York, U.S.A.) June 10, 1932, No. 16488. Convention date, June 12, 1931. [Class 39 (i).] In discharge devices, such as cathode-ray and X-ray tubes, in which a beam of electrons is produced by a cathode surrounded by a focussing device, a support for the focussing device passes through the envelope and is joined to the envelope by a bellows so that the position of the focussing device relatively to the cathode is adjustable from the exterior without disturbing the vacuum. To permit adjustment of both the diameter and the direction of the beam, the focussing device 17, Fig. 2, is mounted on three support rods 20 each connected to an end-plate 18 of the envelope 1 by bellows 22 and each adjustable by compressing or expanding the bellows by a nut 24. The cathode filament 15 in a molybdenum sleeve 15c is adjustable axially by a bellows 32 and nut 40. The device 17 is a copper toroid with rounded edges and its supports 20 are guided in a plate 29 carried by a tube 26 shielding the enclosed parts from discharges. In a cascade tube of the type described in Specification 322,662, [Class 39 (i), Electric lamps, Arc &c.], and comprising a tubular electrode 5, Fig. 1, between the cathode and the anode, the adjustment of the focussing device 17 is made until no current flows to the electrode 5 and until the beam falls in the desired position on a window 9 at the end of a brass anode extension 7. Cathoderays or X-rays emerge from the window according to the nature of the anode. The window may be a thin tungsten plate on the back of which a layer of copper is cast in a vacuum. The window may be cooled by water or other fluid circulated from pipes 11 to a brass cell through which the rays emerge. The electron beam may be concentrated by a coil 12 supported from a wall 131 impervious to X-rays. A tube 14 leads to a vacuum system. The tube is supplied as shown from an induction coil 50 fed through an interrupter 53 from a transformer 52, regulation being effected by an autotransformer 54. A corona shield 3 is provided.