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Proceedings Paper

Reflectance calibrations of AXAF witness mirrors using synchrotron radiation: 2 to 12 keV
Author(s): Dale E. Graessle; Anna M. Clark; Jonathan J. Fitch; Bernard Harris; Daniel A. Schwartz; Richard L. Blake
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Paper Abstract

For the past six years, a high-accuracy reflectance calibration system has been under development at the National Synchrotron Light Source at Brookhaven National Laboratory. The system utilizes Los Alamos National Laboratory's Beamlines X8A and X8C. Its purpose is to calibrate the reflection efficiencies of witness coupons associated with the coating of the eight mirror elements composing the High Resolution Mirror Assembly for NASA's Advanced X-ray Astrophysics Facility (AXAF). During the past year, measurements of reflectances of numerous iridium- coated witness flat mirrors have been obtained to a relative statistical precision of 0.4 percent, and an overall repeatability within 0.8 percent in the overlapping energy regions. The coating processes are strikingly repeatable, with reflectances in the 5-10 keV range for off-end witness flats nearly always being within 1 percent of one another, excluding interference fringes. The comparison reflectances between flats obtained from qualification coating runs and production runs of the Wolter Type I mirror elements are in turn nearly equal, indicating that the qualification run witness flats provide a good representation of the flight optics. Results will produce a calibration of AXAF with extremely good energy detail over the 2-12 keV range, which includes details of the M-absorption edge region for Ir. Development of the program to cover 0.05-2 keV continues.

Paper Details

Date Published: 19 July 1996
PDF: 14 pages
Proc. SPIE 2805, Multilayer and Grazing Incidence X-Ray/EUV Optics III, (19 July 1996); doi: 10.1117/12.245107
Show Author Affiliations
Dale E. Graessle, Smithsonian Astrophysical Observatory (United States)
Anna M. Clark, Smithsonian Astrophysical Observatory (United States)
Jonathan J. Fitch, Smithsonian Astrophysical Observatory (United States)
Bernard Harris, Smithsonian Astrophysical Observatory (United States)
Daniel A. Schwartz, Smithsonian Astrophysical Observatory (United States)
Richard L. Blake, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 2805:
Multilayer and Grazing Incidence X-Ray/EUV Optics III
Richard B. Hoover; Arthur B. C. Walker, Editor(s)

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