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

S. L. O'Dell, R. F. Eisner, J. J. Koiodziejczak, M. C. Weisskopf, J. P. Hughes, L. P. VanSpeybroeck

Research output: Contribution to journalConference articlepeer-review

17 Scopus citations


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). Subsequent visual inspection of the mirror (under grazing incidence illumination) and scanning electron microscopy of tape lifts from the mirrors provides qualitative support for this conclusion. 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 1x104 (for grain radii between 0. 1 jim and 10 j.tm), and that the rms surface-roughness is approximately 0.7 nm (for spatial frequencies between 1 mm1 and 1000 mm1).

Original languageEnglish (US)
Pages (from-to)171-182
Number of pages12
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Jan 21 1993
Externally publishedYes
EventMultilayer and Grazing Incidence X-Ray/EUV Optics for Astronomy and Projection Lithography 1992 - San Diego, United States
Duration: Jul 22 1992 → …

All Science Journal Classification (ASJC) codes

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


Dive into the research topics of 'X-ray evidence for particulate contamination on the AXAF VETA-1 mirrors'. Together they form a unique fingerprint.

Cite this