Optical design and optimization study of metrology sector at high energy photon source

X-ray metrology, including the metrological calibration of X-ray detectors, optical elements and sources, is important for many frontier science, such as X-ray astronomy, EUV-lithography, plasma physics. Among many types of X-ray sources, synchrotron-radiation is considered perfect for X-ray metrology, mainly due to that arbitrarily X-rays specifications can be tailored to meet the demands of metrological calibration of X-ray detectors and optical elements. As a consequence, many metrology beamlines around the world are built, upgrading or to be constructed, including the metrology sector to be constructed at High Energy Photon Source (HEPS). One reasonable way to access good metrological data is using a stable X-ray beam, which means that beam position as well as flux should be as constant as possible and the beamline configuration should be simple and robust to reduce the uncertainty from beamline itself. In addition, the spectral purity of monochromatic X-rays is another crucial factor for X-ray metrology, which means stray X-rays and harmonic X-rays must be as low as possible. Many measures are taken to satisfy these requirements. An optical design of the metrology sector optimized for synchrotron-radiation-based- metrology is described here. The metrology sector, ranging from 50 eV to 20 keV, will be set up to meet the growing needs of X-ray metrology in China. All beamlines’ configurations are simple and easy to use, with an acceptable ratio of high-order harmonics and stray X-rays, which can be under 1% in the entire energy range.