The Low Energy high intensity heavy ion Accelerator Facility (LEAF), independently developed by the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), passed the expert panel acceptance inspection organized by the National Natural Science Foundation of China on December 9.

A heavy-ion accelerator can accelerate ions heavier than alpha particles. With the upgrading of ion accelerators and the evolution of accelerator technologies, frontier research in ion beam physics has continuously deepened human understanding of the world, and related application technologies have been widely adopted in various fields. 

As the world's first stand-alone low-energy, high-intensity, heavy-ion accelerator facility, LEAF holds broad application prospects in frontier interdisciplinary research fields, such as atomic physics, nuclear astrophysics, and nuclear energy materials.

Featuring multifunctionality and miniaturization, LEAF comprises several subsystems, including a 45 GHz superconducting highly-charged electron cyclotron resonance (ECR) ion source, a high-voltage platform, a high-intensity multi-charge-state beam analysis and preparation system and a continuous-wave radiofrequency quadrupole (RFQ) heavy-ion accelerator. 

"LEAF can provide intense heavy-ion beams and mixed ion beams of various charge states from light to heavy elements, offering numerous advantages such as high beam intensity, high charge state, diverse ion species, and a wide range of energy variations," said ZHAO Hongwei, the chief scientist of the project and an academician of CAS.

After nearly 10 years of hard work, the researchers at IMP overcame a series of technical challenges in the production and low-energy acceleration of intense highly-charged heavy-ion beams.

For the first time, the researchers applied Nb₃Sn superconducting magnets to ECR ion sources, and successfully developed the 45 GHz highly-charged ECR ion source with the highest magnetic fields and microwave frequency. Using this newly developed ion source, the produced beam current intensity of ²⁰⁹Bi³⁵⁺ reached 350 microamperes, setting a new world record.

"The ECR ion source we developed can produce a beam intensity more than twice that of similar devices in the world, laying a solid foundation for developing next-generation high-intensity heavy-ion accelerators," said Prof. SUN Liangting from IMP, who led the superconducting ion source development for LEAF. 

The researchers also developed a high-intensity continuous-wave RFQ heavy-ion accelerator, capable of accelerating and stably operating highly-charged heavy-ion beams at the milliampere level.

With LEAF, scientists are expected to conduct pioneering experimental research on low-energy, highly-charged ion collisions. And they will be able to directly measure some key nuclear reaction cross-sections for the nuclear burning processes in various stellar objects, aiming to solve some long-standing scientific issues in nuclear astrophysics. 

In addition, LEAF can also be used to conduct fast evaluation and screening of nuclear irradiation resistant materials, facilitating the development of new materials with excellent radiation resistance and addressing the urgent needs of the new-generation nuclear energy development.

Figure 1. Schematic Diagram of LEAF (Image by IMP)

Figure 2. LEAF (Image by IMP)

Figure 3. 45 GHz superconducting ECR ion source (Image by IMP)