GB1405256A - Electron multipliers - Google Patents

Abstract

1405256 Image intensifier and converter tubes MULLARD Ltd 21 March 1973 [20 April 1972] 1813/72 Heading HID An image intensifier or converter comprises an envelope with input window W 1 carrying a photocathode PC, an output window W 2 carrying a luminescent display screen S combined with a conductive layer, an interposed channel plate, a first insulating layer D 1 on the channel plate input face which layer does not obstruct the channels, a second insulating layer D n on the output face, the channel plate being in contact with both windows via the insulating layers over its working area so that the plate acts as a rigid spacer between windows in withstanding the external atmospheric pressure forces. Contact may be over a continuous area surrounding channel ends, or there may be a contact area after every fourth or fifth row or columns of channels, for example. Continuous and laminated channel plate constructions are described by reference to previous Specifications. The laminate of Fig. 1 includes metal dynode plates M (n2)2 , M (n-1) , and M (n) separated by insulators D (e.g. of glass). The apertures may alternatively be of curved profile, and the channel need not be straight and/or normal to the faces. Insulator D is hidden from electrons by the conductor skirts, and the channel plate forms part of the air-tight envelope. Arrays may be square, triangular, or hexagonal. Steps in the fabrication of the tube assembly are outlined, and glass elements W 1 -D 1 may be bonded by In seals after pre-metallization for example, while W 2 may be bonded by enamel or In. Silver chloride seals may replace the In seals. Further, the insulators D, D 1 , D n may be enamel initially thicker than required, and then heated and compressed on bonding. Terminal lugs T to the dynodes are staggered (Fig. 1B, not shown), while connection to screen S and cathode PC may be via the In seals, or conducting strips for enamel seals. In Fig. 2 (not shown), separate wall W 3 provides the vacuum seal between W 1 - W 2 , and the terminal lugs are connected to pins Ta, Tb. Fabrication steps are again outlined, and the plate may be bonded to the output window by a low temperature process using silicate cement. The photocathode and screen layers may extend beyond the matrix to further electrical contact pins. Plate M(1) holes may have a wider cone angle than the other plate holes. For X-rays, a CsI phosphor may be between PC and W 1 , the latter may be a thin metal sheet and can be flat. The screen S may be separate recessed elements (Sd), (Fig. 3, not shown), with conductive screen layer Ea. Layers D 1 , D 2 , D n may be resistive, and may be arrays of lines or islands. Plate dimensions are given.