Physicists in China have passed an important milestone towards an accelerator-driven sub-critical (ADS) system, a novel accelerator design for advanced energy and other technologies. On 2 July, teams working on “Injector I” at the Chinese Academy of Sciences’ Institute of High Energy Physics (IHEP) in Beijing succeeded in accelerating a proton beam to an energy of 10.11 MeV with a peak beam current of 10.5 mA in pulse mode. “This is a major breakthrough for the ADS Injector I after five years of hard work by scientists from the Institute of High Energy Physics, and marks a new step for high-current proton-linear-accelerator technology worldwide,” explains IHEP deputy-director Weimin Pan.

ADS technology directs high-energy protons towards a heavy target, whereupon spallation reactions produce dozens of neutrons for every proton. A portion of these neutrons may then be used to drive a sub-critical nuclear reactor, with the remaining neutrons used for nuclear-waste transmutation or other applications. Indeed, the past 10 years has seen the development of various combined ADS systems aiming at different applications – including proposals to generate nuclear power from thorium instead of uranium fuel.

The Chinese ADS Injector I is the world’s first proton accelerator to use low-β superconducting “spoke cavities”. It consists of an electron cyclotron resonance (ECR) ion source, a 325 MHz radio-frequency quadrupole accelerator, a superconducting linac containing 14 spoke cavities in two cryomodules, beam transport lines and a beam dump. During beam commissioning, the proton beam reached a final energy of 10.5 MeV with a beam current of 10.11 mA. The cavities achieved an accelerating gradient of 7 MV m–1 and beam transmission through the superconducting linac was 100%.

“This is an important focus of development for ADS accelerators, which lays the foundations for the future Chinese ADS project,” says Pan.