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Proceedings Paper

Analysis of iridium reflectance measurements for AXAF witness mirrors from 2 to 12 keV
Author(s): Jonathan J. Fitch; Dale E. Graessle; Bernard Harris; John P. Hughes; Dan T. Nguyen; Daniel A. Schwartz; Richard L. Blake
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Paper Abstract

For the best flexibility in ground and on-orbit calibration modeling of the AXAF telescope over its entire field of view, including off-axis calibration evaluations, AXAF synchrotron reflectance calibrations require that the measured reflectance data be reduced to optical parameters analogous to n and k. We have developed a method for AXAF witness mirror analysis which is a modification of the NKFIT optical constants algorithm published by D.L. Windt. The algorithm assumes uniform layer thicknesses using a recursive, exact formation of Fresnel's equations, with a modified Debye-Waller roughness correction factor. The recursion formula has been modified to include an explicit double-precision formulation. The results of most of the fits of AXAF calibration measurements yield residuals less than 1 percent of the reflectance value levels down to R approximately .03. The precision of the measurements is smaller still, which compromises the (chi) 2 fitting algorithm; however, the results will most likely prove adequate for AXAF witness mirrors calibrated in the 5-12 keV range. Coating density determined from the refractive index n is approximately 98.5 percent of the bulk for iridium. Derived coating thicknesses are extremely consistent with the photon energy, giving still more significant calibration information to the program.

Paper Details

Date Published: 19 July 1996
PDF: 12 pages
Proc. SPIE 2805, Multilayer and Grazing Incidence X-Ray/EUV Optics III, (19 July 1996); doi: 10.1117/12.245108
Show Author Affiliations
Jonathan J. Fitch, Smithsonian Astrophysical Observatory (United States)
Dale E. Graessle, Smithsonian Astrophysical Observatory (United States)
Bernard Harris, Smithsonian Astrophysical Observatory (United States)
John P. Hughes, Smithsonian Astrophysical Observatory (United States)
Dan T. Nguyen, Smithsonian Astrophysical Observatory (United States)
Daniel A. Schwartz, Smithsonian Astrophysical Observatory (United States)
Richard L. Blake, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 2805:
Multilayer and Grazing Incidence X-Ray/EUV Optics III
Richard B. Hoover; Arthur B. C. Walker, Editor(s)

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