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Proceedings Paper

Transfer of autocollimator calibration for use with scanning gantry profilometers for accurate determination of surface slope and curvature of state-of-the-art x-ray mirrors
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Paper Abstract

X-ray optics, desired for beamlines at free-electron-laser and diffraction-limited-storage-ring x-ray light sources, must have almost perfect surfaces, capable of delivering light to experiments without significant degradation of brightness and coherence. To accurately characterize such optics at an optical metrology lab, two basic types of surface slope profilometers are used: the long trace profilers (LTPs) and nanometer optical measuring (NOM) like angular deflectometers, based on electronic autocollimator (AC) ELCOMAT-3000. The inherent systematic errors of the instrument’s optical sensors set the principle limit to their measuring performance. Where autocollimator of a NOM-like profiler may be calibrated at a unique dedicated facility, this is for a particular configuration of distance, aperture size, and angular range that does not always match the exact use in a scanning measurement with the profiler. Here we discuss the developed methodology, experimental set-up, and numerical methods of transferring the calibration of one reference AC to the scanning AC of the Optical Surface Measuring System (OSMS), recently brought to operation at the ALS Xray Optics Laboratory. We show that precision calibration of the OSMS performed in three steps, allows us to provide high confidence and accuracy low-spatial-frequency metrology and not ‘print into’ measurements the inherent systematic error of tool in use. With the examples of the OSMS measurements with a state-of-the-art x-ray aspherical mirror, available from one of the most advanced vendors of X-ray optics, we demonstrate the high efficacy of the developed calibration procedure. The results of our work are important for obtaining high reliability data, needed for sophisticated numerical simulations of beamline performance and optimization of beamline usage of the optics. This work was supported by the U. S. Department of Energy under contract number DE-AC02-05CH11231.

Paper Details

Date Published: 2 October 2019
PDF: 16 pages
Proc. SPIE 11109, Advances in Metrology for X-Ray and EUV Optics VIII, 1110905 (2 October 2019); doi: 10.1117/12.2529519
Show Author Affiliations
Ian Lacey, Lawrence Berkeley National Lab. (United States)
Kevan Anderson, Lawrence Berkeley National Lab. (United States)
Jeff Dickert, Lawrence Berkeley National Lab. (United States)
Ralf D. Geckeler, Physikalisch-Technische Bundesanstalt (Germany)
Andreas Just, Physikalisch-Technische Bundesanstalt (Germany)
Frank Siewert, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (Germany)
Brian V. Smith, Lawrence Berkeley National Lab. (United States)
Valeriy V. Yashchuk, Lawrence Berkeley National Lab. (United States)


Published in SPIE Proceedings Vol. 11109:
Advances in Metrology for X-Ray and EUV Optics VIII
Lahsen Assoufid; Haruhiko Ohashi; Anand Asundi, Editor(s)

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