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Proceedings Paper • Open Access

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC
Author(s): Michel Bougoin; Didier Castel; Franck Levallois

Paper Abstract

For Herschel SiC primary mirror purpose, a new approach of comparative CTE measurement has been developed; it is based on the well known bimetallic effect (“biceramic” in this case) and also optical measurements. This method offers a good CTE comparison capability in the range of 170-420K (extensible to 5-420K) depending of the thermal test facilities performance, with a resolution of only 0.001 μm/m.K. The Herschel primary mirror is made of 12 SiC segments which are brazed together. The CTE of each segment has been compared with the one of a witness sample and no visible change, higher than the measurement accuracy, has been observed. Furthermore, a lot of samples have been cut out from a spare segment, from different places and also from all X, Y and Z direction of the reference frame. No deviation was seen in all of these tests, thus demonstrating the very good homogeneity, reproducibility and isotropy of the Boostec® SiC material. Some recent literature about SiC material measurements at cryogenic temperature shows a better behaviour of Boostec® SiC material in comparison with other kind of SiC which are also candidate for space optics, in particular for isotropy purpose. After a review of the available literature, this paper describes the comparative CTE measurement method and details the results obtained during the measurement campaigns related to Herschel project.

Paper Details

Date Published: 20 November 2017
PDF: 7 pages
Proc. SPIE 10564, International Conference on Space Optics — ICSO 2012, 1056410 (20 November 2017); doi: 10.1117/12.2309208
Show Author Affiliations
Michel Bougoin, BOOSTEC (France)
Didier Castel, Astrium (France)
Franck Levallois, Astrium (France)

Published in SPIE Proceedings Vol. 10564:
International Conference on Space Optics — ICSO 2012
Bruno Cugny; Errico Armandillo; Nikos Karafolas, Editor(s)

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