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In order to research the influence of the quantity of the Micro-Channel Plates (MCP) on the detectable threshold
of the ultraviolet image intensifier tube, the wide spectrum image intensifier gain tester produced by Nanjing University
of Science and Technology is employed to test the relation curves between self-made one single MCP ultraviolet image
intensifier tube, two double MCP ultraviolet image intensifier tubes, and photocathode incidence radiation illumination
respectively. With reference to the 3rd-generation low-light image intensifier failure theory, if the radiation gain of the
ultraviolet image intensifier tube is defined as 1,000cd/m2, the tube will lose the effect of image intensification, when
the corresponding photocathode incidence radiation illumination will be the minimum detectable threshold. Viewed
from the test results, the minimum detectable threshold of the single MCP ultraviolet image intensifier tube is 3.0×10-6
W/m2, with the radiance gain linear interval between 3.0×10-6 W/m2 ～4.6×10-5 W/m2; and that of the double MCP ultraviolet image intensifier tubes is 4×10-7 W/m2, with the radiance gain linear interval between 4.0×10-7 W/m2 ～2.0×10-5 W/m2. The test results were analyzed on the basis of the MCP self-saturation effect, concluding that the saturation current density of the single-unit MCP is a fixed , but there may be certain difference among the saturation current density of different MCPs due to different materials and manufacturing processes. The test results show that the maximum of the radiation gain linear interval of the three ultraviolet image intensifier tubes are at the magnitude of 10-5 W/m2, and the non-significant differences also verified the theory. In the double MCP ultraviolet image intensifier tubes, the photocathode-produced photocurrent is multiplied in passing the first MCP and then reaches the second MCP, so the second MCP will reach the state of current saturation earlier than the first MCP, making the minimum detectable threshold of the double MCP ultraviolet image intensifier tubes is lower than that of the single ultraviolet image intensifier tube by one order of magnitude, with the linear gain interval increasing by one magnitude, and the absolute of the corresponding radiation gain of the same radiation illumination within the linear gain interval increasing by 10
times, verifying that the double MCPs can detect much lower and weaker ultraviolet radiation and realize the high gain
theory. The research results has certain guiding effect towards the promotion and application of the double ultraviolet
image intensifier tubes, and has great significance on enhancing the high ultraviolet radiation detection and imaging
technology.
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