X-ray crystal polygon-mirror and its application for absolute calibration of angular positions

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An x-ray crystal polygon-mirror is much compact than that of an optical polygonmirror. In practices, the x-ray crystal polygon-mirror is a small silicon cylinder with diameter of 1mm and height of 10mm. For conveniently using this small device, the crystal cylinder was scraped from a quadratic prism with a pedestal of the sijte of 10mm cube remained. Axis of the cylinder is <110> crystal direction, where the crystal polygon-mirror has 340 diffractions for x-ray with wavelength of 0.06968nm.There is a little difference on the angular position of x-ray diffractiop under the boundary condition of a flat crystal surface and a cylinder surface. But it was conformed practically that under the condition where the axis of the crystal polygonmirror is parallel to that of the rotary table within a quantity of sub-milliradilan, the peak position of x-ray diffractions from the cylinder crystal is consistent to that of the flat surface with position accuracy of sub-arc-second.340 Diffractions from the x-ray crystal polygon-mirror were detected) using an x-ray beam of synchrotron radiation with wavelength of 0.06968nm. Fallowing the calibration process, we evaluated a precise rotary table equipped with rotary encoder within accuracy of 1 arc-sec.