Structure design and thermal optical analysis of a cryogenic collimator

Cryogenic collimator is an important component of low temperature environment simulation test system. This paper introduces the structural design and thermal optical analysis for a cryogenic collimator, with a focal length of 4m and optical aperture diameter of 400mm. The difference between the alignment temperature and actual operating temperature is nearly 200°C. According to the athermal optical design, the same material is used for the mirror and support structure to reduce the thermal stresses caused by the change of temperature. According to the thermal optical analysis, the temperature variation could cause the maximum shrinkage of 6.3mm along the optical axis. The MTF of the system could still meet the requirement with predictable shape changes of mirror surfaces.