China Marks Progress on High Energy Photon Source

The construction of the High Energy Photon Source (HEPS) at the Chinese Academy of Sciences has marked a milestone as electron beams with currents exceeding 10 milliamperes (mA) were successfully stored in the HEPS storage ring. The achievement signifies the completion of the accelerator complex and the beginning of beam commissioning.

The facility is the first high energy synchrotron radiation light source in China and is expected to become one of the brightest fourth-generation synchrotron radiation facilities worldwide. HEPS will serve as a research platform for material science, chemical engineering, biomedicine, and other fields.

The HEPS accelerator complex consists of an injector and a diffraction-limited storage ring. The injector includes a 500 megaelectron volt (MeV) linear particle accelerator and a 6 gigaelectron volt (GeV) booster. The commissioning of the injector was completed in 2023, meeting the performance objectives and marking the start of routine operation.

A computer rendering of the High Energy Photon Source (HEPS) accelerator. The project began construction in 2019 following its listing as one of China’s large research infrastructure projects in the country’s 13th Five-Year Plan. Courtesy of IHEP.

The electron storage ring, with a circumference of 1360.4 m, is the main component of the HEPS accelerator complex. It stores ultra-low emittance electron beams. The storage ring is composed of 48 seven-bend achromats, meticulously designed to achieve a horizontal natural emittance of less than 60 pm·rad at a beam energy of 6 GeV.

The HEPS storage ring is one of the largest synchrotron light source accelerators in the world and the largest in China. Its primary function is to store high-energy, high-quality electron beams and generate high-performance synchrotron radiation. According to reporting by Xinhua News Agency, China’s largest state-run media outlet, a total of 1776 magnets, over 2500 power supplies, and 578 electron beam position monitors have been installed on the storage ring, with over 100,000 control signals.

HEPS began storage ring commissioning on July 23 this year, following the completion of fabrication, installation, and joint conditioning of all equipment in the storage ring.

At the time, electron beams were transmitted through the entire high-energy transport line connecting the booster and the storage ring on the same day, and then injected into the storage ring. The whole procedure was completed within two hours. About four hours later, electron beams successfully traveled more than one circle in the storage ring, facilitated by tuning a few correctors near the injection point.

Screenshot of the High Energy Photon Source (HEPS) accelerator status displays on Aug, 18 showing a beam current of about 12 mA. The facility, under the auspices of the Institute of High Energy Physics (IHEP) at the Chinese Academy of Science, is expected to be fully operational by the end of 2025. Courtesy of IHEP.

According to Pan Weimin, project director of HEPS, the quick achievement indicated that the joint conditioning was effectively completed, and all equipment was aligned and powered with high precision as expected.

By July 29, 2024, electrons could circulate in the ring more than a dozen times. Subsequently, the radiofrequency cavities started operation, coupled with further optimization of the injected beam parameters and storage ring settings, which resulted in the beam circulating more than one hundred times. The sextupoles were then turned on and gradually ramped to their design gradients, leading to the first stored beam with a current of approximately 50 μA and a lifetime of over 10 seconds on Aug. 6.

Multi-bunch injection was later realized with the stored beam parameters and those of injected bunches continuously optimized. On Monday, HEPS successfully achieved beam with current of well above 10 mA, representing a hundred-fold improvement over the previous result.

“Commissioning of the HEPS storage ring will continue in the next few months, with the aim to achieve higher beam currents with sufficiently long beam lifetime for vacuum conditioning and beamline commissioning,” said Jiao Yi, deputy director of the HEPS accelerator division.

As one of China’s key scientific and technological infrastructure projects set out in the nation’s 13th Five-Year Plan, construction of HEPS began in Huairou Science City on June 29, 2019.

The project is expected to be ready for operation by the end of 2025.