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Proceedings Paper

Correlation Between The Performance And Metrology Of Glancing-Incidence Synchrotron-Radiation Mirrors Containing Millimeter-Wavelength Shape Errors
Author(s): P. Z. Takacs; R. C. Hewitt; E. L. Church
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Paper Abstract

This paper concerns the properties of a set of ellipsoidal x-ray mirrors manufactured for use at the National Synchrotron Light Source at Brookhaven. The objective is to compare the results of functional tests made at x-ray wavelengths and at glancing incidence with predictions based on laboratory measurements of their surface shapes made with a Wyko profiling microscope. The functional tests of the fully-illuminated mirrors indicated unacceptable image widths of roughly 300 μrad. Subaperture tests involving 1.5-mm-long segments of the mirror surface gave images which consisted of 2 to 5 sharp sub-images with separations of 17 - 50 μrad and individual widths comparable with the measurement point-spread function. Profile measurements indicated that the surfaces had a strong periodic ripple with an rms amplitude of about 85 Angstroms and a period of about 1.7 millimeters. When these ripple parameters are fed into the Fresnel-Kirchhoff diffraction integral we pre-dict that the idealized image should break up into fine structure consisting of approximately 7 lines, uniformly spaced 17 pm apart; in excellent agreement with the results of the subaperture functional tests. The wash-out of the sub-image fine structure in the case of the fully-illuminated mirrors is attributed to the presence of longer-wavelength surface errors than are included within the bandwidth of the Wyko measurements. The present analysis is unusual in that it involves the prediction of the effects of shape errors with amplitudes which lie between the smooth-surface limit, where the intensity in the image plane is a mapping of the power spectral density of the error, and the rough-surface limit, where it is a mapping of its slope distribution function.

Paper Details

Date Published: 20 April 1987
PDF: 6 pages
Proc. SPIE 0749, Metrology: Figure and Finish, (20 April 1987); doi: 10.1117/12.939850
Show Author Affiliations
P. Z. Takacs, Brookhaven National Laboratory (United States)
R. C. Hewitt, Exxon Corporation (United States)
E. L. Church, USA ARDEC (United States)


Published in SPIE Proceedings Vol. 0749:
Metrology: Figure and Finish
Bruce E. Truax, Editor(s)

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