Overview of the High Energy Photon Source Accelerators

Abstract The High Energy Photon Source (HEPS), Asia’s first fourth-generation synchrotron light source, marks a major milestone in China’s accelerator development. As a greenfield facility initiated in 2019, HEPS consists of a three-stage accelerator complex, including a 500 MeV S-band linear accelerator, a 454-meter full-energy booster, and a 1.36-kilometer storage ring employing a modified hybrid 7-bend achromat lattice. This design achieves an ultra-low emittance of approximately 35 pm·rad in the storage ring, enabling near-diffraction-limited synchrotron radiation in the hard X-ray regime. In addition, a low-energy beam transport line transfers electron bunches from the Linac to the booster, while two high-energy beam transport lines enable beam delivery between the booster and the storage ring in both directions. During construction, the technical feasibility of the full-energy injection chain was verified after successful beam commissioning of both the Linac and the booster. The commissioning of the storage ring has now been successfully completed, with key performance parameters─including the design beam energy of 6 GeV, horizontal natural emittance lower than 100 pm·rad, beam current exceeding 100 mA, orbit stability better than 20%, brightness of the synchrotron light approximately 4 × 1021 photons/s/mm2/mrad2/0.1%BW, and capability of providing higher than 300 keV X-rays─achieved through meticulous beam performance optimization. Looking ahead, HEPS will focus on enhancing beam stability and reliability, providing an unprecedented high-brightness platform for multidisciplinary research in materials science, biology, and energy, thereby propelling scientific discovery in China and globally.