Patent GB-1402549-A (GB)
Title: Electron multipliers
IPC: H01J43/22
Filed: 1971-12-23
Abstract: 1402549 Electron multipliers MULLARD Ltd 9 Nov 1972 [23 Dec 1971] 59966/71 Heading HID A channel plate electron multiplier (e.g. for image intensifiers, c.r.t.s, and TV display applications) comprises a laminated stack of perforate metal conductor layers (M (n-2) , M (n-1)  ...) with regular arrays of apertures, and a separator (D) between each layer which is discontinuous in that it does not completely surround the individual apertures in the conductor layers, each separator being an array of elements regularly distributed across the plate and less conductive than the metal layers, the latter being sufficiently conductive and secondary emissive to constitute discrete dynodes. The (d) is continuous separators reduce exposure to electrons and produce wider tolerances in expansion coefficients. Separators are preferably thinner than the conductors, the latter may be of sheet metal, and apertures may be circular or rectangular. The separators may be insulative or resistive, and external potentiometers may not be required. Dimensions and angles are given for Fig. 1 with line separators and the conical forms may alternatively have curved profiles. Aperture arrangements may vary (Figs. 3A, 3B, not shown) and separator d may be waved to accord with the pattern of apertures C. There may be less than one separator channel (Figs. 4A-4D, not shown). Figs. 5, 6 (not shown) include separator dots. For dots and apertures of equal size, one metal plate may be used as template for separator deposition on an identical metal plate. Depositions may be by screen printing, electrophoresis, anodizing and evaporation. Glass separators may be applied to one side of mild steel plates and plates bonded together by partial melting of separators. Spacing may be by two types of separator, one for bonding and one for spacing, the latter of high m.p. glass and machined after application. Resistive separators may be high Pb content glass (e.g enamel type glasses) surface reduced in hydrogen, or vitreous carbon made from plastic like materials converting to C on high temperature firing, or Al or Al alloy plates with aluminium oxide separators. In Fig. 1, dynode M(1) may be of greatest open area as by increased aperture diameter or by increasing its thickness outwardly. Secondary emission of some or all plates may be enhanced by an emissive coating (e.g. on the first conductors on the input side). Conductor layers (Fig. 7, not shown) with input and output electrodes M(1) and M(n) are staggered preventing feedback of orthogonal electrons and optical and ion feedback from a display screen. Channels may be curved, or stacks oppositely tilted, or tilted and orthogonal stacks combined (e.g. Fig. 8, not shown) with dot or line separators. A thin membrane may be across each channel entrance, e.g. a photoemissive layer (patent Specification 1,154,515) or electron permeable conductor membranes (patent Specification 1,175,599) produced by methods in patent Specification 1,319,850. Photoemissive areas on or in contact with the input electrode may be as in patent Specification 1,090,406. Other patent Specifications are referred to. The plates may be used in colour display applications as in patent Specification 1,402,547.