GB1401969A - Electron multipliers - Google Patents

Abstract

1401969 Electron multipliers MULLARD Ltd 2 Oct 1972 [17 Nov 1971] 53371/71 Heading H1D An electron multiplier channel plate is formed as a laminated structure of alternate conductor layers M and resistive separator layers D, with aligned apertures providing the channels, whereby charge build-up on the layers D is prevented. The conductor layers may be of steel plate, with the walls of the apertures coated with secondary emissive material, and the separator layers of a lead oxide containing glass which has been heated, in hydrogen, after fabrication, to provide a resistive surface lead layer, or of vitreous carbon. Alternatively, the conductor layers may be of aluminium, and the separator layers of aluminium oxide coated with a resistive layer. In low current applications, the resistive layers may be exposed to the electron trajectories, such that they supply a portion of the secondary emission, and the current flowing through the resistive layers may be employed to maintain the potentials of the successive conductive plates, dispersing with the use of an external resistor chain. For high current applications, e.g. when the channel plate is scanned by a cathode ray beam, the construction is arranged such that the resistive layers are substantially concealed from the electron trajectories. Methods of fabrication discussed include: coating apertured steel conductor plates on one side with glass, etching the glass through the plate apertures, and heating a stack of the plates until the glass melts and bonds them together; and a variety of methods involving the combined use of photo and etch resists, e.g. anodizing one surface of an aluminium plate, coating the anodized layer and the other surface of the aluminium layer with a photo-resist and an etch resist, respectively, exposing the photo-resist to a dot pattern, etching through the alumina and aluminium layers, removing the resists, and applying a resistive coating to the exposed channel surfaces of the alumina. If maximum concealment of the resistive material D from the electron trajectories is required, it may be etched back still further subsequent to the assembly and bonding together of a stack of plates, Fig. 8. Successive plates of a stack may be staggered, to give curved or slanting channels (Figs. 9 and 10, not shown); an electron-permeable conductive membrane, or a photo-emissive layer, may be provided at the channel entrances; and square section channels may be employed.