X-ray evidence for particulate contamination on the AXAF VETA-I mirrors

Stephen L. O'Dell; Ronald F. Elsner; Jeffery J. Kolodziejczak; Martin C. Weisskopf; John P. Hughes; Leon P. Van Speybroeck

doi:10.1117/12.140551

21 January 1993 X-ray evidence for particulate contamination on the AXAF VETA-1 mirrors

Stephen L. O'Dell, Ronald F. Elsner, Jeffery J. Kolodziejczak, Martin C. Weisskopf, John P. Hughes, Leon P. Van Speybroeck

Author Affiliations +

Proceedings Volume 1742, Multilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography; (1993) https://doi.org/10.1117/12.140551
Event: San Diego '92, 1992, San Diego, CA, United States

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).

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Stephen L. O'Dell, Ronald F. Elsner, Jeffery J. Kolodziejczak, Martin C. Weisskopf, John P. Hughes, and Leon P. Van Speybroeck "X-ray evidence for particulate contamination on the AXAF VETA-1 mirrors", Proc. SPIE 1742, Multilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography, (21 January 1993); https://doi.org/10.1117/12.140551

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