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Proceedings Paper

Low emittance, semi-transparent coating for cryogenic window applications
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Paper Abstract

A warm window surface with a relatively high (>50%) surface emittance can add significant undesired heat loading into a cryogenic test chamber. However, a front surface coating that consists of a very thin adherent layer of evaporated Cr that is overcoated with about 7nm of evaporated Au has been demonstrated to reduce the inherently high emittance of a glass or sapphire window surface down to about 14%, while maintaining a visible transmittance in excess of 55%. The coating possesses reasonably good adhesion and cleaning durability when deposited onto glass or sapphire substrates and has survived multiple temperature cycles between 316K and 20K. The addition of a single layer anti-reflection coating, such as reactively evaporated SiOx, to the otherwise uncoated exterior surface of a cryogenic window produced a further increase in visible wavelength transmittance without altering window emittance. This paper will present measured reflectance, transmittance, and emittance data for the Cr + Au window surface coating relevant to a cryogenic window application.

Paper Details

Date Published: 17 September 2009
PDF: 8 pages
Proc. SPIE 7439, Astronomical and Space Optical Systems, 743912 (17 September 2009); doi: 10.1117/12.829351
Show Author Affiliations
James B. Heaney, Stinger Ghaffarian Technologies, Inc. (United States)
Maria Nowak, NASA Goddard Space Flight Ctr. (United States)
Manuel Quijada, NASA Goddard Space Flight Ctr. (United States)
Felix Threat, NASA Goddard Space Flight Ctr. (United States)
Joseph Stock, Stinger Ghaffarian Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 7439:
Astronomical and Space Optical Systems
Penny G. Warren; James B. Heaney; Robert K. Tyson; Michael Hart; E. Todd Kvamme; Cheryl J. Marshall, Editor(s)

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