Progress of the High Energy Photon Source construction

The High Energy Photon Source (HEPS) project is one of the national major scientific infrastructure programs approved by the National Development and Reform Commission for construction during the "13th Five-Year Plan" period. The construction of the project began in June 2019 in the Huairou Science City, Beijing, with a construction period of 6.5 years, and has been carried out by the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences. This project, including constructing the accelerators, beamlines and experiment stations, and auxiliary facilities, aims to build a 4thgeneration synchrotron radiation light source providing high brightness X-ray beams in the high energy region. This highquality hard X-ray beam is a crucial "probe" that can be widely used in research ranging from the nanoscale single-atom level to the macroscopic scale. There are three accelerators, a 0.5 GeV linear accelerator (Linac), a 0.5-6.0 GeV booster and a 6.0 GeV storage ring, in the HEPS for driving the synchrotron radiation. The Linac, composed of normal conducting accelerating structures, is the electron source and provides the first stage of acceleration for the electron beams. The electron beam accelerated by the Linac is transferred to the booster via a transport line named LTB. The booster further accelerates the beam to 6.0 GeV, and feeds this beam to the storage ring via another transport line named BTR. The booster can also accept electron beams from the storage ring at 6.0 GeV, and merges these returned beams with those newly accelerated ones to produce big bunches for the storage ring. The storage ring was designed using the most advanced technique, the multi-bend achromatic (MBA) structure, in the field of synchrotron facility. As presented by the HEPS preliminary design report, the storage ring could focus the electron beam to an emittance as low as 35 pm rad and generate X-ray beam with a brightness in 1022 ph s(-1) mm(-2) mrad(-2) (0.1%BW)(-1) level. The design beam current in the storage ring is 200 mA. After lattice and orbit correction, the dynamic aperture is 3 mm and 2 mm in horizontal and vertical planes, respectively. The Linac and booster have been installed and commissioned, and the installation of the storage ring is mostly finished and has been prepared for the beam commissioning. As the results of the commissioning, the Linac provided more than 7 nC single-bunch current with energy spread less than 0.45% and emittance less than 60 nm rad at its downstream end. The booster achieved more than 5.0 nC single-bunch current at 6.0 GeV. All the key parameters of both the Linac and the booster achieved by the commissioning well meet their design values. The storage ring could host as many as 90 beamlines and end-stations for user experiments. In this phase-I stage, 14 public beamlines and end-stations have been constructed. Most beamlines adopt undulator/wiggler radiations. The installation and testing of these beamlines and end-stations have been advancing as scheduled. After accomplished, the HEPS would be one of the brightest synchrotron radiation light sources over the world, and become an important research platform for various kinds of research.