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High Accuracy, Absolute, Cryogenic Refractive Index Measurements of Infrared Lens Materials for JWST NIRCam using CHARMSThe current refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF2, and ZnSe. In order to provide the instrument s optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA GSFC, densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Measurement methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented along with estimates of uncertainty. Coefficients for second order polynomial fits of measured index to temperature are provided for many wavelengths to allow accurate interpolation of index to other wavelengths and temperatures.
Document ID
Document Type
Conference Paper
Leviton, Douglas
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Frey, Bradley
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Subject Category
Instrumentation And Photography
Meeting Information
SPIE Conference(San Diego, CA)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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