The Circular Electron Positron Collider (CEPC) research team officially released its technical design report (TDR) for the accelerator complex on Dec. 25. It is the world’s first TDR for a Higgs factory based on a circular electron–positron collider. Its completion marks an important milestone in development of the CEPC.

The concept of the CEPC was proposed by Chinese high-energy physicists in September 2012, with a priority on Higgs particles at a beam energy of 125 GeV and coverage of energies at Z (45 GeV), W (80 GeV), and ttbar (180 GeV). Additionally, the CEPC tunnel is able to accommodate the Super Proton–Proton Collider (SPPC). After five years of effort on design and R&D, the CEPC team released its conceptual design report in November 2018. After another five years of endeavor, the CEPC team has now completed the accelerator TDR, which is available on the website for particle physics preprints (arXiv: 2312.14363). 

Over the past five years, the CEPC team has further optimized the accelerator design.  Luminosities and other performance specifications of the accelerator are all at the most advanced level internationally and meet physics objectives. With funding from various sources, the team has carried out R&D on key technologies necessary for the CEPC. Significant progress has been made in areas such as the superconducting RF system and RF power source, elevating their capabilities to the highest global level. Prototypes for mass production, including magnets, vacuum components, and electrostatic deflectors, have been developed, meeting or exceeding the required specifications. Additionally, conventional technologies, such as the electron linac, RF system, beam diagnostics, injection and extraction system, cryogenics, alignment, and mechanics, have been successfully applied in large-scale accelerator facilities including BEPCII and HEPS, which were constructed by the host institute of CEPC—IHEP.

Based on these achievements, the CEPC team has completed the accelerator TDR, which has been reviewed by international committees on technology and cost evaluation chaired by Dr. Frank Zimmermann from CERN and Dr. Leonid Rivkin from PSI, respectively. The civil construction cost has been reviewed by a domestic committee chaired by Deputy Chief Engineer Zongyin Guan from the China Renewable Energy Engineering Institute. The committees expressed great appreciation for the TDR’s achievements, saying, “The key technologies for CEPC have been developed. Prototypes meeting or exceeding the specifications are available. The CEPC team is on track to launch an engineering-design effort.” The CEPC International Advisory Committee, chaired by Prof. Brian Foster, also supported the review committee conclusions and endorsed the research plan and objectives for the next stage of CEPC development.

Following the formal release of the TDR, the CEPC will begin work on the engineering design report in 2024 and be ready to begin construction during the 15th Five-year Plan, with the goal of starting CEPC operation around 2035.

The CEPC accelerator TDR represents the efforts and achievements of thousands of domestic and overseas scientists and engineers. It has received extensive support and recommendations from the high energy physics community, with input by more than 1100 authors. CEPC plays an important role in future plans of the international high energy physics community, facilitating extensive and in-depth collaboration in particle physics worldwide to explore the frontiers of science and cutting-edge technologies. The success of CEPC will deepen our understanding of matter, energy, and the universe to an unprecedented degree.