12 September 2007 A second generation low stress cryogenic mount for space-borne lithium fluoride optics
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Single crystal Lithium Fluoride has been base-lined as one of the optical materials for the Near Infra-Red Camera (NIRCam) on the James Webb Space Telescope (JWST). Optically, this material is outstanding for use in the near IR. Unfortunately, this material has poor mechanical properties, which make it very difficult for use in any appreciable size on cryogenic space based instruments. In addition to a dL/L from 300K to 30K of ~-0.48%, and a room temperature CTE of ~37ppm/K, the material deforms plastically under relatively small tensile loading. This paper will update a paper presented in 2005 on the same optical mount [1]. The mount has been proven via vibration and thermal-vacuum testing to successfully mount large (70 mm-94 mm) Lithium Fluoride optics for application in space. An overview of Lithium Fluoride material properties and characteristics is given and updated yield strength test data is provided and discussed. A design limit load is determined for the material based on strength values from the literature as well as independent testing. The second generation mount design is then presented along with test data and results. Finally, the test results are discussed showing survival and performance of the optic and mount during cool-down to the operational thermal environment.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
E. Todd Kvamme, E. Todd Kvamme, Michael Jacoby, Michael Jacoby, "A second generation low stress cryogenic mount for space-borne lithium fluoride optics", Proc. SPIE 6692, Cryogenic Optical Systems and Instruments XII, 66920I (12 September 2007); doi: 10.1117/12.742095; https://doi.org/10.1117/12.742095


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