Located on the Renping peninsula in Huizhou, south China's Guangdong province, the High Intensity heavy-ion Accelerator Facility (HIAF) successfully passed the process acceptance inspection in July and entered trial operation phase.

It is the world's first "three-in-one" advanced heavy-ion research facility integrating a superconducting linear accelerator, a synchrotron and a storage ring, Yang Jiancheng, deputy director of the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS) and chief engineer of HIAF, said.

HIAF provides heavy-ion beams with the highest pulsed beam intensity currently available worldwide and is equipped with a nuclear mass spectrometer with the highest measurement accuracy, providing a world-class research platform for cutting-edge nuclear science and major applications of heavy ions.

New solution

What exactly is HIAF? Yang made a comparison, saying it is both a giant microscope and an ion cannon. A heavy-ion accelerator enables man-made high-speed ion beams to crash targeted materials precisely to generate a large amount of particle debris. Scientists analyze the debris to explore the micro structure inside the materials.

The idea of building HIAF was proposed by IMP in 2009, and the HIAF was constructed in 2018. The first beam was generated in 2025. The superconducting ion source of HIAF lies 13 meters under earth. "This is the world's first fourth-generation superconducting electron cyclotron resonance (ECR) ion source developed by our team. We have increased the microwave frequency to 45 gigahertz, setting a world record for the highest beam current achieved by an ECR ion source," Shen Guodong, head of the accelerator systems office of HIAF technology center, said.

The ion source operates in a pulsed-beam mode. It is like precisely controlling an engine's throttle and ignition timing, enabling the ion beam to reach its optimal operating state at the very moment it is launched, Shen said.

But the innovations go far beyond this. To accumulate a large number of particles into an ultra-high-current beam, the particles must be kept orderly and not be allowed to spread chaotically. This has been a world-class challenge, with no major breakthroughs internationally for more than two decades.

The team developed a new approach combining six-dimensional phase-space painting and independent-clock stacking. The method not only expands the injection process from the two-dimensional space used in previous approaches to six dimensions, but also overcomes the limitation imposed by the circumference ratio.

This breakthrough has increased HIAF's beam-current accumulation gain tenfold over the previous international high, while reducing beam losses by an order of magnitude.

Breaking the record

To make the heavy-ion beams travel smoothly, the research team needed to build a vacuum tunnel, and they built an ultra-thin-wall ultra-high-vacuum chamber with an internal support frame, the first of its kind internationally.

The chamber has an ultra-thin outer wall, just 0.3 millimeters thick —about the thickness of three sheets of A4 paper stacked together. Inside, a 3D-printed titanium alloy frame, only about four millimeters thick, provides structural support. The design is not only strong and resistant to eddy currents, but also significantly reduces construction costs.

The team also developed a new pulsed power supply that overcame the challenges of extremely rapid current changes and high-precision control during pulsed operation. The power supply achieves an internationally record-high current slew rate of 38,000 amperes per second, while maintaining a tracking error of less than 0.2 amperes.

"It's like a supercar traveling at about 140,000 kilometers per hour on the Beijing-Shanghai expressway, while never straying more than 20 centimeters from its lane throughout the journey," Wang Xiaojun, deputy director of the power supply office of HIAF technology center, said.

In addition, HIAF has achieved full beam transmission through its two-kilometer beamline in just 16 hours, setting a new international record for the speed of beam commissioning at comparable facilities. The beam intensities of HIAF's typical oxygen-ion and bismuth-ion beams have both set new international records, raising the previous international highs threefold and 7.5-fold, respectively.

Many experiments that previously required months or even years to accumulate sufficient data could in the future be completed in days or even hours.

Prospective directions

As the world's first large-scale scientific facility to combine a superconducting linear accelerator, a fast-cycling synchrotron and a cascade storage ring, HIAF's unique three-in-one configuration offers two key advantages.

It can accelerate all types of ions, enabling research across a wide range of scientific disciplines. Moreover, its ultra-high beam intensity means that it can provide richer experimental data and produce more nuclides that were previously difficult to generate, helping researchers discover new physical phenomena.

"With this large scientific facility, Chinese scientists could potentially synthesize new elements," Yang said with optimism.

In addition to exploring the limits of atomic nuclei, once HIAF becomes operational, it will also focus on elucidating nuclear astrophysical processes, advancing nuclear energy development, and promoting multidisciplinary applications.

For example, HIAF can be used for the anti-radiation performance test of spacecraft, promoting the development of nuclear energy and functional materials. It can also play a crucial role in improving people's livelihoods, such as advancing heavy-ion cancer treatment, the development of radiopharmaceuticals, crop breeding and food preservation.

A new-generation, more accessible heavy-ion radiotherapy system developed through the application of advanced HIAF technologies has been deployed at the Huizhou Central People's Hospital.

Notably, the tunnel for the superconducting linear accelerator is nearly 400 meters long and more than 100 meters of accelerator equipment has been installed, with over 200 meters of space reserved for future upgrades. This forward-looking design enables large scientific facilities to adapt seamlessly to the ever-changing research needs of the future, Shen said.