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Proceedings Paper

Molecular contamination study of iridium-coated x-ray mirrors
Author(s): Dale E. Graessle; T. H. Burbine; Jonathan J. Fitch; William A. Podgorski; Jiahong Zhang Juda; Ronald F. Elsner; Stephen L. O'Dell; J. M. Reynolds
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Paper Abstract

We have completed extensive synchrotron reflectivity measurements on several iridium mirrors which were intentionally coated with thin layers (100 angstroms or less) of polyethylene, a hydrocarbon contaminant. The purpose was to verify theoretical predictions of alterations in reflection efficiency of an iridium surface for various thicknesses of hydrocarbon contamination, and to evaluate the acceptability of attainable upper limits of such contamination for the mirrors aboard NASA's Advanced X-ray Astrophysics Facility (AXAF). Although the deposition of such thin layers is problematic with no systematic guarantee of uniform thickness or density, successful analysis by modeling the contaminant as a uniform surface layer may be done, within a limited X-ray energy range. The M-edges of iridium are significantly affected by the polyethylene layers. For the most part, contamination increases the reflectance in the M-edge range over that of bare iridium, although cross-over points between contaminated and uncontaminated mirrors occur at several angles relevant to AXAF. However, calibratability of the reflectance is a more significant issue than X-ray mirror efficiency. We present the modeling results for three thicknesses of polyethylene, and discuss the implications for the performance of AXAF mirrors and their calibratability.

Paper Details

Date Published: 11 November 1994
PDF: 15 pages
Proc. SPIE 2279, Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics, (11 November 1994); doi: 10.1117/12.193173
Show Author Affiliations
Dale E. Graessle, Smithsonian Astrophysical Observatory (United States)
T. H. Burbine, Smithsonian Astrophysical Observatory (United States)
Jonathan J. Fitch, Smithsonian Astrophysical Observatory (United States)
William A. Podgorski, Smithsonian Astrophysical Observatory (United States)
Jiahong Zhang Juda, Smithsonian Astrophysical Observatory (United States)
Ronald F. Elsner, NASA Marshall Space Flight Ctr. (United States)
Stephen L. O'Dell, NASA Marshall Space Flight Ctr. (United States)
J. M. Reynolds, NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 2279:
Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics
Richard B. Hoover; Arthur B. C. Walker Jr., Editor(s)

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