24 December 2002 Topography measurement of nanometer synchrotron optics
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Abstract
The technological limit on the beam quality when modern synchrotron radiation sources are used is determined by the geometrical accuracy of the optical components. This in turn is limited by the accuracy of the measuring technique which is within the range of up to 0.05 arcsec rms for one meter mirror length, which corresponds (in the absence of waviness) to an uncertainty of the topography of 5 nm rms. If the topography can be measured with higher accuracy, modern methods of ion beam processing allow the surface to be postprocessed with a high resolution of depth. We will present first tests with a novel measuring device which allows deflectometric measurements by the ESAD principle (Extended Shear Angle Difference) to be carried out. The basic item of this device is a commercial electronic autocollimator (AC) whose exit aperture is tripartite. By suitable evaluation one is in consequence able to simultaneously determine the angle information belonging to three surface points situated next to one another. According to the ESAD method, the angular topography can be completely reconstructed from two sets of angular difference data. The uncertainty of measurements of angular difference is transferred with a factor close to 1 to that of the set of reconstructed angle. First measurements show a reproducibility of about 25 milli-arcsec rms at a time of integration of 0.4 seconds per point. With this set-up, in the first order, no guide errors, vibrations or air turbulences enter.
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Jens Illemann, Jens Illemann, Ralf D. Geckeler, Ralf D. Geckeler, Ingolf Weingartner, Ingolf Weingartner, Carsten Schlewitt, Carsten Schlewitt, Bernd Grubert, Bernd Grubert, Olaf Schnabel, Olaf Schnabel, } "Topography measurement of nanometer synchrotron optics", Proc. SPIE 4782, X-Ray Mirrors, Crystals, and Multilayers II, (24 December 2002); doi: 10.1117/12.450982; https://doi.org/10.1117/12.450982
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