With the installation of its electron gun, the High Energy Photon Source (HEPS), the first high-energy synchrotron radiation light source in China and one of brightest fourth-generation synchrotron radiation facilities over the world, is brought into its installation phase on June 28, 2021.

The HEPS facility is composed of the accelerators, beamlines, end stations, and support facilities, etc. The accelerator system, as one of the main components of the light source, consists of three accelerators, a storage ring with electron beam energy of 6 GeV, a booster and a Linac. The Linac, with a total length of about 49 m, is the injector for the booster. It comprises an electron gun, a bunching system, and a main accelerator. The electron gun is the first piece of the accelerator equipment installed in the accelerator tunnels.

The electron gun mainly comprises the gun cavity, cathode-grid assembly and accessory structures. It provides high intensity and high quality electron beams for the Linac. As one of the key technical challenges encountered in the HEPS project, the in-house developed cathode-grid assembly porotype has been under test and yielded promising results.

As one of the China's key scientific and technological infrastructure projects during the 13^th Five-year Plan, the HEPS began its construction in Huairou District, Beijing on June 29, 2019. Over the last two years, the construction on the HEPS project has been advanced on schedule. Scientific equipment purchases and fabrication are in full swing. The accelerator hardware systems, including the magnets, RF cavities, linac power source and microwave equipment, have been being manufactured. A series of performance tests on these hardware systems are underway.