Off-axial cold collimator with a 600-mm aperture as part of thermovacuum test facility

Дмитриев И.Ю., Завацкая А.В., Линский П.М. Сиразетдинов В.С. Внеосевой охлаждаемый коллиматор с апертурой 600 мм в составе термовакуумного испытательного стенда // Оптический журнал. 2024. Т. 91. № 9. С. 40–52. http://doi.org/10.17586/1023-5086-2024-91-09-40-52

Dmitriev I.Y., Zavatskaya A.V., Linsky P.M., Sirazetdinov V.S. Off-axial сooled collimator with a 600-mm aperture as part of thermovacuum test facility [in Russian] // Opticheskii Zhurnal. 2024. Т. 91. № 9. С. 40–52. http://doi.org/10.17586/1023-5086-2024-91-09-40-52

Subject of study. Thermal modes and optical characteristics of an off-axial two-mirror collimator with cooled-down mirrors. Coincidence degree of the collimator elements temperature values obtained computationally and experimentally. Optical quality of the collimator. Aim of study. Design and set-up of the collimator with a cooled-down lens mirrors for expansion of the thermovacuum test facility functionality by decreasing thermal background inside the vacuum chamber and creating conditions for testing optoelectronic devices with photodetectors in the background-limited performance mode. Method. Collimator elements’ temperatures were determined on the basis of the developed thermophysical model of the "collimator lens – thermostat – chamber" system. The model is based on heat balance equations derived for each element of the system in a stationary mode. Experimentally, temperatures of the system elements were recorded in certain checkpoints. Optical quality of the collimator was controlled by measuring radiation energy concentration factor in the autocollimation image plane of the collimator’s radiation point-source. Main results. The suggested configuration of the "collimator lens – thermostat – chamber" system produces temperature range from –45 to–80 °C for the radiative shields, cooling collimator lens mirrors down to the given temperature –33 °С, subject to their minimized thermal deformation. The produced cooled collimator has high optical quality: radiation energy concentration factor in the autocollimation image plane of the collimator’s radiation "point-source" is 70% for the object imitation channel and 75% for the background channel. Practical significance. Functionality of the operating thermovacuum facility has been considerably increased: testing conditions for Earth remote sensing equipment with photodetectors in background-limited performance mode have been created. Thermophysical model of the "collimator lens – thermostat – chamber" system has been developed.