Molecular contamination study of iridium-coated x-ray mirrors

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

doi:10.1117/12.193173

11 November 1994 Molecular contamination study of iridium-coated x-ray mirrors

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

Author Affiliations +

Proceedings Volume 2279, Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics; (1994) https://doi.org/10.1117/12.193173
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

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.

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Dale E. Graessle, T. H. Burbine, Jonathan J. Fitch, William A. Podgorski, Jiahong Zhang Juda, Ronald F. Elsner, Stephen L. O'Dell, and J. M. Reynolds "Molecular contamination study of iridium-coated x-ray mirrors", Proc. SPIE 2279, Advances in Multilayer and Grazing Incidence X-Ray/EUV/FUV Optics, (11 November 1994); https://doi.org/10.1117/12.193173

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