The main component of the image intensifier is the input screen. At the front end of the enhancement tube is a large input screen, which is closely attached to the photocathode (there is a very thin transparent layer between the two).
Input screen: The input screen is coated with phosphor. The thicker the phosphor layer is, the stronger the brightness is, but the resolution decreases due to the scattering and reflection of light; the thinner the phosphor layer is, the lower the brightness is. So cesium iodide phosphor is used to solve this contradiction. Compared with the earlier zinc-cadmium sulphide phosphors, cesium iodide phosphors can improve the X-ray absorptivity, fluorescence efficiency, influence resolution and match the characteristics of photocathode spectra.
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