Analysis of iridium reflectance measurements for AXAF witness mirrors from 2 to 12 keV

J. J. Fitch, Dale E. Graessle, Bernard Harris, John P. Hughes, Dan T. Nguyen, Daniel A. Schwartz, Richard L. Blake

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


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 χ 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.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsRichard B. Hoover, Arthur B.Jr. Walker
Number of pages12
StatePublished - 1996
Externally publishedYes
EventMultilayer and Grazing Incidence X-Ray/EUV Optics III - Denver, CO, USA
Duration: Aug 5 1996Aug 6 1996

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering


OtherMultilayer and Grazing Incidence X-Ray/EUV Optics III
CityDenver, CO, USA

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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