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Proceedings Paper

X-ray evidence for particulate contamination on the AXAF VETA-I mirrors
Author(s): Stephen L. O'Dell; Ronald F. Elsner; Jeffery J. Kolodziejczak; Martin C. Weisskopf; John P. Hughes; Leon P. Van Speybroeck
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Paper Abstract

X-ray testing of the AXAF outer mirror pairs, in the VETA-1 configuration, reveals a point spread function (PSF) with unexpectedly large wings at low energies. Although the angular dependence in the wings of the PSF is close to that expected for diffractive scattering from surface roughness, the energy dependence differs substantially. Analyses of the observed X-ray PSF, images near ring focus, and single-quadrant images at conjugate focus suggest that the excess scattering observed at low X-ray energies results from diffractive scattering by relatively small grains (as small as a few tenths micrometer in radius). We develop a simple model for the contribution of scattering by particulates to the PSF. Merging this model with that for scattering by surface roughness, we fit the combined model to the observed energy-dependent PSF, in order to estimate parameters and associated uncertainties characterizing the grain-size distribution and the surface-roughness power spectral density. In particular, we find that the fractional coverage of the mirrors by particulates is approximately 1 x 10 exp -4 (for grain radii between 0.1 and 10 microns), and that the rms surface-roughness is approximately 0.7 nm (for spatial frequencies between 1/mm and 1000/mm).

Paper Details

Date Published: 21 January 1993
PDF: 12 pages
Proc. SPIE 1742, Multilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography, (21 January 1993); doi: 10.1117/12.140551
Show Author Affiliations
Stephen L. O'Dell, NASA Marshall Space Flight Ctr. (United States)
Ronald F. Elsner, NASA Marshall Space Flight Ctr. (United States)
Jeffery J. Kolodziejczak, NASA Marshall Space Flight Ctr. (United States)
Martin C. Weisskopf, NASA Marshall Space Flight Ctr. (United States)
John P. Hughes, Smithsonian Astrophysical Observatory (United States)
Leon P. Van Speybroeck, Smithsonian Astrophysical Observatory (United States)

Published in SPIE Proceedings Vol. 1742:
Multilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography
Richard B. Hoover; Arthur B. C. Walker II, Editor(s)

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