GB507448A - Improvements in or relating to electron multipliers - Google Patents

Abstract

507,448. Electron multipliers. FARNSWORTH TELEVISION, Inc. May 23, 1938, No. 15284. Convention date, June 22, 1937. [Class 39 (i)] A multiplier comprises a substantially rectangular chamber which has one open side 15, Fig. 3, two solid secondary electron - emissive sides 9, 10 which are opposite and adjacent, respectively, the open side, and an electron permeable wall 14, and means for directing electrons through the permeable wall to impact the solid walls at a point adjacent the junction thereof. A number of chambers are mounted on the pinch 16, Fig. 1, and electrons from a source, e.g. a filamentary cathode 3 surrounded by a control electrode 4, are directed onto the curved edge 24 of the first chamber through an aperture 6 in a shield 5. The aperture is small when used for scanning an electron image. A focusing field is formed between adjacent chambers to concentrate the electrons onto the junction of the solid walls. Flanges 17 screen the gaps between the chambers, and an output electrode 19 is mounted between the last chamber and a secondary-electron-emissive electrode 18. A solid helical member 21, or a coating on the wall, preferably connected to the cathode, absorbs positive ions. The solid walls of the chamber are formed of silver which is oxidized and coated with caesium, and the permeable wall is formÚd of knitted tungsten wire; apertures in the end walls facilitate activation of the secondary-emitting surfaces.