The International Cost Review Meeting for the Technical Design Report (TDR) (Phase-II) of the Circular Electron Positron Collider (CEPC) Accelerator was held in Hong Kong, China, from September 11 to 15. Focusing on the cost of each system of the CEPC Accelerator, the meeting was hosted by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences and organized by the Hong Kong University of Science and Technology. An 8-member review committee was formed with experts from six countries including Switzerland, Japan, Germany, the United Kingdom, France and Italy. Professor Leonid RIVKIN, a senior scientist at the École Polytechnique Fédérale de Lausanne (EPFL) and Deputy Director of the Paul Scherrer Institute (PSI) in Switzerland, served as the Chair of the Review Committee. All committee members are world-leading experts and renowned scholars in the fields of accelerator physics and technology, as well as cost estimation for international large scientific facilities.

Academician Wang Yifang, Director of IHEP and Chair of the CEPC Steering Committee, delivered a welcome speech. He pointed out that building on the CEPC team's accelerator design in the TDR and the conclusions of the completed international technical review (Phase-I), the team looks forward to the independent and professional considerations and opinions of the review panel on the cost estimation of the accelerator systems.

The meeting focused on the cost of each system of the CEPC Accelerator. Researcher Lou Xinchou, Project Manager of the CEPC, first gave a presentation on the general overview of the CEPC and the conclusions of the international technical review (Phase-I). Researcher Li Yuhui, Deputy Director of IHEP and Convener of the CEPC Accelerator, delivered a report on the methods and basis for the cost estimation of the CEPC Accelerator. The meeting featured more than 20 presentations on cost estimation covering various systems of the CEPC Accelerator, including physical design, radio frequency, power source, magnet, power supply, control, beam diagnostics, vacuum, mechanics, radiation protection, alignment, and general operation. In addition, an internal reporting and communication meeting was held via video link with Professor John Osborne, Chair of the International Cost Review Panel for CEPC Civil Engineering and a senior civil engineering expert for the FCC study at CERN, to share insights with the cost review committee.

During the five-day meeting, all committee members completed an intense and heavy workload and finalized the preliminary review comments. The committee concluded that based on the existing accelerator design, the cost basis for each system is sufficient and the estimation is reasonable. At the same time, the review committee put forward targeted suggestions for the cost estimation work of each professional field, and the final review comments will be released in mid-October.

The accelerator team will further optimize and improve the CEPC Accelerator Technical Design Report by integrating the final comments from the international technical review and cost review. The convening of this review meeting will lay a solid foundation for the mass production and installation of prototypes for each system in the future, and make adequate preparations for the industrialization schedule.