GB1205565A - Improvements in or relating to electron guns - Google Patents

Abstract

1,205,565. Electron guns. THE RANK ORGANISATION Ltd. 22 Sept., 1967 [28 Sept., 1966], No. 43364/66. Heading H1D. An electron gun comprises, adjacent the planar cathode 9, an accelerating electrode 14 having a penetration factor of less than 0À7 and adapted to provide unipotential surfaces parallel to the cathode surface, a shielding electrode 18 being disposed in front of the electrode 14 to prevent other electrodes from altering the unipotential surfaces; an electron beam uniform over its cross-section and devoid of any crossover, is produced. In one example the electrode 14 is a solid metal plate 0À005 inch thick with a central aperture of 0À020 inch diameter disposed 0À004 inch from the cathode and biased 5 volt positive to the cathode. Electrode 18 is disposed 0À005 inch from electrode 14 and may be sufficiently thick in relation to the diameter of its central aperture to screen the space adjacent to the cathode; otherwise the aperture may be covered with a mesh. Further electrodes 20, 22 and 29-36 may be provided, of which electrodes 32, 34, 35 and 36 are at 320 volts arid the others at 1030 volts. Electrode 36 is connected to a graphite coating 38 the other end of which is connected to a high resistance helix 42. In operation modulating potentials may be applied to either of the electrodes 14 and 18. The tube shown has a fluorescent screen 6, but the gun may be used in a vidicon, an orthicon, a travelling wave tube, a storage tube or a plural-beam tube . Reference has been directed by the Comptroller to Specification 1,119,931.