Cryogenic system for interferometric measurement of dimensional changes at 40 K: design and performance

Peter Blake; Franklin Miller; Tim Zukowski; Edgar R. Canavan; Allen Crane; Tim Madison; David Miller

doi:10.1117/12.741002

17 September 2007 Cryogenic system for interferometric measurement of dimensional changes at 40 K: design and performance

Peter Blake, Franklin Miller, Tim Zukowski, Edgar R. Canavan, Allen Crane, Tim Madison, David Miller

Author Affiliations +

Proceedings Volume 6692, Cryogenic Optical Systems and Instruments XII; 669207 (2007) https://doi.org/10.1117/12.741002
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

This report describes the facility, experimental methods, characterizations, and uncertainty analysis of the Cryo- Distortion Measurement Facility (CDMF) at the Goddard Space Flight Center (GSFC). This facility is designed to measure thermal distortions of structural elements as the temperature is lowered from 320K to below 40 K over multiple cycles, and is capable of unattended running and data logging. The first measurement is the change in length and any bending of composite tubes with Invar end-fittings. The CDMF includes a chamber that is efficiently cooled with two cryo-coolers (one single-stage and one two-stage) rather than with liquid cryogens. Five optical ports incorporate sapphire radiation shields - transparent to the interferometer - on each of two shrouds and a fused silica vacuum-port window. The change in length of composite tubes is monitored continuously with displacement-measuring interferometers; and the rotations, bending, and twisting are measured intermittently with theodolites and a surface-figure interferometer. Nickel-coated invar mirrors and attachment mechanisms were developed and qualified by test in the CDMF. The uncertainty in measurement of length change of 0.4 m tubes is currently estimated at 0.9 micrometers.

Citation Download Citation

Peter Blake, Franklin Miller, Tim Zukowski, Edgar R. Canavan, Allen Crane, Tim Madison, and David Miller "Cryogenic system for interferometric measurement of dimensional changes at 40 K: design and performance", Proc. SPIE 6692, Cryogenic Optical Systems and Instruments XII, 669207 (17 September 2007); https://doi.org/10.1117/12.741002

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