Variable gain X-ray image intensifier tube

An X-ray image intensifier tube is described comprising a silicon diode array imaging target which, on the electron bombarded site, is provided with a deeply diffused phosphorus n+ layer covered with a metallic buffer layer. This invention relates generally to X-ray image intensifier tube and more specifically to a silicon diode array imaging target for such X-ray intensifier. Conventional silicon intensified target (SIT) operates with incident electrons accelerated to energies from 2.5 to 10 keV, corresponding to target gains of approximately 1 to 2000, respectively. In practice, the photocathode of the X-ray image intensifier tube is held at a negative potential and the photo electrons strike the target which is near ground potential. The disadvantage of the standard silicon intensified target lies in the fact that in the range required for an X-ray image intensifier tube having photocathode voltages of minus 19 kilovolts to minus 25 kilovolts, the target gain is too high and the X-ray flux into the image intensifier must therefore be kept low to avoid saturating the output signal of the target. An X-ray image intensifier tube operated in this manner has a low signal-to-noise ratio