Stand for Certification of X-ray Optical Elements and Systems for Synchrotron Applications

The article describes an X-ray optical certification setup based on a microfocus X-ray tube, a Kirkpatrick-Baez (KB) collimating system, and a Gpixel2020BSI matrix semiconductor detector. To minimize X-ray beam scattering and intensity loss due to absorption in air, vacuum-tight tubes with compton windows are installed between the microfocus X-ray tube and the KB system, and between the KB system and the detector. Pumping is performed by an oil-free fore-vacuum pump. The setup that has been developed allows for studying the X-ray optical scheme of two-mirror monochromators to determine the deformation of the beam wave front at their outputs, and to calibrate the movement of high-precision mechanical tables. The setup also allows for studying the focusing properties of the Kirkpatrick-Baez system, itself, namely, measuring the size of the focus spot and calibrating the piezo-drives of the mirrors. As a result of adjusting the collimating system, we obtained a converging beam, but this did not prevent us from measuring the wave front broadening upon reflection from the substrates for a two-mirror monochromator. Two substrates made of single-crystal silicon Si(100) were studied. It was shown that upon reflection from the substrate after chemical-mechanical polishing (CMP) only, the reflected beam, due to mirror shape errors, broadened by 18 μm, while after chemical-mechanical polishing and correction of local shape errors using an ion beam, the broadening was reduced to 11 μm, which corresponds to an angular error of the mirror at a level of 3 μrad. This is 7 times less than the angular divergence of the beam at the output of the collimating system, due to the size of the radiation source.