Hard x‐ray detector with an MCP image intensifier working in the 100 keV 1 MeV x‐ray range

We present a high gain x‐ray image intensifier with high sensitivity in the 1 MeV x‐ray range and a good spatial resolution developed in order to improve the radiographic detection in our experiments. In particular the gold photocathode and MCP thickness have been optimized to give the best trade off between the dose sensitivity and the spatial resolution. The large useful 60‐mm‐diam photocathode set on the MCP input converts the x‐ray emission into electrons that are multiplied in the MCP and proximity focused onto the P11 phosphor screen deposited on a fiber‐optic plate. For x‐ray quanta of 1 MeV energy the x‐ray image converter is more sensitive than the most sensitive x‐ray screen film systems. Using for instance a pulsed x‐ray source we have been able to record pictures of a sphere or of a testing metallic chart for a dose lower than 100 μrad; under these conditions the spatial resolution was greater than 1 lp mm−1 and the dynamic range was still around 10. Using an x‐ray screen film under same input level we have obtained a very low dynamic range and density values actually equal to the noise level. These unique performances fulfill the requirements of a large number of detonic experiments needing a high sensitivity in the 1 MeV x‐ray range.