GB678546A - Improvements in or relating to electron discharge tubes - Google Patents

Abstract

678,546. Cathode-ray tubes. RAULAND CORPORATION. Dec. 22, 1950 [Dec. 23, 1949], No. 31242/50. Class 39 (i). In a cathode-ray ion trap arrangement the anode 27, Fig. 4, is provided with an apertured disc 14 coated with fluorescent material 29 on the side facing the cathode 21 so as to give a visual indication when the beam strikes it, and adjustable magnetic deflecting means are provided for deflecting the beam to pass through the aperture 30 in the disc while the ions are trapped by the anode 27. The luminescent material, preferably zinc silicate activated with manganese, is applied to disc 14 before insertion in the tube by dusting it over a coating of waterglass, a temporary mask being placed over aperture 30 during the process. The inside wall of the anode cylinder adjacent disc 14 may also be coated with luminescent material. Accelerating electrode 26 and anode 27 have oblique facing edges so as to provide an electric field with a transverse component, and the electrons are restored to the axis by means of a magnet 31, a second magnet 32 correcting for any overshooting caused by the magnet 31. Magnets 31, 32 are split spring rings permanently magnetized with diametrically opposite poles, and are mounted on resilient support 33; they may be rotated independently or rotated or moved axially together by movement of support 33, and are normally arranged to give oppositely directed fields. Control electrode 22, accelerating electrode 26 and anode 27 are secured to glass supporting rods 24 by metal lugs 25, 28.