Investigation of Parasitic Background IR Radiation Levels on a Photodetector Surface in a Vacuum Cryostat

The results of experimental and numerical simulations studying the stray background levels on an IR photodetector surface in a vacuum cryostat with a cylindrical diaphragm are presented in the article. The stray background value was investigated by the direct measurement with a second thermal camera pointed at the surface of the first camera’s hybrid assembly. The limitations of the experimental method are the accuracy of measuring the background level on the surface of the photodetector. It is necessary to use a cooled second thermal camera as a measuring instrument since if the temperature of the photodetector in it is higher than the temperature of studied surface, and its radiation reflected from the IR photodetector does not allow reliable results to be obtained. This method of the research makes it possible to identify technological imperfections in the design of the studied cryostats. Numerical simulation makes it possible to optimize the shape and the design of cold diaphragms, but it does not allow to analyze the contributions of various sources of parasitic radiation in the cryostat. This requires additional modeling and simulation.