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Cryolite Overcoated Aluminum Reflectors for Far-Ultraviolet Spectroscopy Aluminum (Al) mirrors are conventionally protected with metal-fluoride coatings (e.g., MgF2, LiF, or AlF3) immediately after deposition to prevent oxidation and preserve its far-ultraviolet (FUV) spectral efficiency. However, the resulting FUV reflectance of the aluminum reflector is limited by the metal-fluoride overcoat film index of refraction, morphology, stoichiometry, and its absorption cut-off in the lower end of the FUV spectra. Cryolite (sodium hexafluoroaluminate, Na3AlF6) emerges as a potential candidate to preserve the aluminum FUV reflectance due to its relatively lower index of refraction in the visible to ultraviolet; therefore, allowing for the thin-film design of highly spectral efficient reflectors over a wide spectral range. We investigate the use of cryolite in aluminum reflector FUV coating design. The deposited aluminum reflector overcoated with cryolite will be examined in terms of spectral efficiency and environmental durability. The deposited cryolite overcoat will be evaluated in terms of optical constants and structural properties. Preliminary results have shown that the use of cryolite as an overcoat to protect aluminum would yield unprecedented results as an optimal Hydrogen Lyman-alpha (HLyα) spectral line reflector, with experimental reflectance values >96%.
Document ID
20230013085
Acquisition Source
Goddard Space Flight Center
Document Type
Presentation
Authors
Javier Del Hoyo
(Goddard Space Flight Center Greenbelt, Maryland, United States)
Luis Rodriguez De Marcos
(Catholic University of America Washington D.C., District of Columbia, United States)
J Hennessy
(Jet Propulsion Lab La Cañada Flintridge, California, United States)
M Batkis
(Goddard Space Flight Center Greenbelt, Maryland, United States)
C Bos
(Intern)
Manuel Quijada
(Goddard Space Flight Center Greenbelt, Maryland, United States)
Date Acquired
September 7, 2023
Publication Date
August 30, 2023
Publication Information
Publisher:
Subject Category
Optics
Meeting Information
Meeting: SPIE Optics and Photonics 2023
Location: San Diego, CA
Country: US
Start Date: August 20, 2023
End Date: August 24, 2023
Sponsors: International Society for Optics and Photonics
Funding Number(s)
WBS: 141108.04.02.01.66
Distribution Limits
Public
Copyright
Portions of document may include copyright protected material.
Technical Review
Professional Review
Keywords
optical coatings
ultraviolet
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