Design and Commissioning of Micro-focusing Biological Macromolecular Beamline (ID02U1A) at HEPS

Abstract The fourth-generation synchrotron radiation sources featuring high-brilliance and low-emittance have brought about more opportunities for macromolecular crystallography beamlines. The High Energy Photon Source (HEPS) represents one of the most brilliant fourth-generation light sources across the world. As one of the 14 Phase-I beamlines at HEPS, the ID02U1A beamline is specifically dedicated to X-ray crystallographic structure determination of biological macromolecules, spanning a tunable energy range of 5.0–18.0 keV. The beamline is designed to deliver a micrometer-scale focused X-ray beam with a photon flux exceeding 1 × 1013 photons/s in a 0.1% bandwidth, thus leveraging its ability to decipher atomic structures of functionally important membrane proteins that are difficult to crystallize and poorly diffract. In order to achieve such high photon flux at a micron-sized spot while maintaining sufficient beam stability, the beamline is specifically equipped with an in-air undulator (IAU), a horizontal-reflection channel-cut monochromator (HCCM), and four sets of transfocators along the optical path. For automated high-throughput data collection, the experimental station is equipped with a commercial diffractometer, sample changer robot and high-frame-rate detector, all of which are integrated into the custom-built data acquisition system Aurora. With the ID02U1A beamline now commissioned and operational, this paper elaborates on its design philosophy and current status.