Low emittance, semi-transparent coating for cryogenic window applications

James B. Heaney; Maria Nowak; Manuel Quijada; Felix Threat; Joseph Stock

doi:10.1117/12.829351

17 September 2009 Low emittance, semi-transparent coating for cryogenic window applications

James B. Heaney, Maria Nowak, Manuel Quijada, Felix Threat, Joseph Stock

Proceedings Volume 7439, Astronomical and Space Optical Systems; 743912 (2009) https://doi.org/10.1117/12.829351
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States

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.

Citation Download Citation

James B. Heaney, Maria Nowak, Manuel Quijada, Felix Threat, and Joseph Stock "Low emittance, semi-transparent coating for cryogenic window applications", Proc. SPIE 7439, Astronomical and Space Optical Systems, 743912 (17 September 2009); https://doi.org/10.1117/12.829351

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