GB1023655A - Electron multiplier - Google Patents

Abstract

1,023,655. Electron multipliers. RADIO CORPORATION OF AMERICA. April 30, 1963 [May 24, 1962], No. 17010/63. Heading H1D. An electron multiplier has a tubular resistive secondary electron emissive coating 14 on the inner wall of the tubular envelope 12, and a central wire electrode 20 of radius in proportion of 1:800- 1000 to the radius of the tubular envelope. A potential gradient is established along the coating by the D.C. source 18 and a high positive voltage is applied to the electrode 20. The coating 14 is also photo-emissive so that the end 17 serves as a photo - cathode. Tensioning spring 22, or an enlarged end of the electrode 20, or a separate tubular electrode 24 forms the collector electrode of the tube. A light shield may be placed around the tube. The primary cathode, however, need not be a photo-cathode. In another embodiment a separate photo-emissive coating is provided at 17 to form the photo-cathode and the central electrode 20 is replaced by a quartz fibre with a resistive coating, e.g. of tin oxide, along which a potential gradient is also established. In a modification the resistive secondary electron emissive coating may be formed as a single or double helix. Conductive secondary electron emissive and possibly also photo-emissive elements may be deposited as a mosaic on the resistive material and, where resistive material is provided in the form of a helix, also on the envelope parts in between the turns of the helix. Alternatively, a resistive coating may be deposited over a resistive helix and a mosaic of conductive secondary electron emissive elements provided on the resistive coating. A resistive secondary emissive and photo-emissive coating may be formed by condensing a thin film of antimony, afterwards reacted with caesium, on a previously evaporated antimony coating. Conductive secondary emissive elements deposited as a mosaic on resistive material may consist of caesium-activated globules of oxidized silver, the resistive material consisting of a thin platinum film or alternatively, of caesiumactivated patches of antimony. A detailed account is given of the necessary equations for use in operating and designing the tube.