GB1319850A - Image intensifiers and the like - Google Patents

Abstract

1319850 Electrode processing MULLARD Ltd 28 Sept 1971 [18 Nov 1970] 54817/70 Heading H1D A membrane obturating the end of each channel of a channel electron multiplier is formed by allowing a liquid to form a meniscus at the mouth of each channel, solidifying the meniscus to form a temporary support on which the membrane is formed, and removing the temporary support. The liquid may be solidified by freezing or it may contain a dispersion of fine particles which are caused to emerge from the liquid and form a surface film by physical means, such as heat, ultrasonics or electrical treatment, or by chemical means such as adding electrolytes or surfactants or charging the pH value. The membrane is preferably of aluminium and may form an input electrode or may be applied after a separate input electrode has been formed. In one process the liquid is an emulsion of poly-2-ethoxyethyl methacrylate in water, the solids content being 0À6%. A channel plate is dipped into the emulsion so that the liquid rises by capillary action and the plate is then inverted over an infra-red lamp the heat from which causes the emulsion particles to form a solid plastic film over the exposed meniscus surface. After drying out the liquid remaining in the channels, the plate is located on a table which rotates in an evacuated chamber whilst a 500Š layer of aluminium is evaporated over the plastic film, and the latter is removed by baking. If a non-reflecting black layer is required, a second aluminium layer can be evaporated through an inert gas on to the first aluminium layer. If the channels have a diameter of less than 100 microns, the process of infra-red heating causes the meniscus to withdraw from the end, and this can be prevented by supporting a mesh 0À5-1 mm above the top surface and filling this space with water to provide a reservoir.