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TY - UNPB AU - Yang, F.G. ED - Schaa, Volker RW ED - Tavakoli, Keihan ED - Tilmont, Manuel TI - Modified Twyman-Green Interferometer for the Sagittal-Focusing Monochromator J2 - Proc. of MEDSI2018, Paris, France, 25-29 June 2018 C1 - Paris, France T2 - Mechanical Engineering Design of Synchrotron Radiation Equipment and Instrumentation T3 - 10 LA - english AB - The sagittally bent monochromator is a desirable optics for hard X-ray beamlines and an important part of the advanced research for High Energy Photon Source (HEPS). The information of the surface figure of the crystal is very important for the optimization of bender. However, it is difficult to measure the shape directly by interferometer or long trace profiler due to very big principal curvature (1/Rs), which distorts the deflectometric probe light therefore affects the accuracy of the measurement. We have developed ex-situ metrology instrument - a low-cost modified Twyman-Green interferometer by using commercial element in our laboratory. The misalignment among the detector, cylindrical sample light and the crystal mirror was adjusted by rotating the interferometer according to the theoretical calculation, which can separate the effect of the misalignment and the distortion of the mirror. The accuracy of the curvature radius (about few mm) is assured by precisely moving the mirror under test. PB - JACoW Publishing CP - Geneva, Switzerland ER -