The Conceptual Design Report (CDR), Volume I – Accelerator for the Circular Electron Positron Collider (CEPC) was published on September 2. The CEPC Accelerator CDR has reached its goal in multiple energy ranges, including the Higgs, W and Z poles.

The CEPC Study Group has been working on the conceptual design of the CEPC since the publication of the Preliminary Conceptual Design Report (Pre-CDR) in March 2015. The Fully Partial Double-Ring with Crab-Waist Collision scheme is the baseline accelerator design used in the CDR. A number of accelerator designs, including Single-Ring Pretzel, Partial Double-Ring, Advanced Partial Double-Ring and Fully Partial Double-Ring, were considered and optimized by the CEPC Study Group. The detailed comparison of various design options and the final choice of the baseline was documented in CEPC-SppC Progress Report – Accelerator, published in April 2017.

The CEPC accelerator team completed the first draft of the current CDR in November 2017. The team soon conducted a preliminary review and revised it. A committee of international experts then reviewed the CDR from June 28-30 at IHEP. In its subsequent report, the committee said it “unanimously congratulates the CEPC team on the completion of the CDR, with remarkable successes in various aspects of the design.” The review committee also said it believes “the CDR has already reached a sufficient level of maturity to allow approval to proceed to a Technical Design Report.” The CEPC Study Group incorporated the comments from the reviewers into the CDR and released the document on September 2.

The CEPC Accelerator CDR comprises 505 pages, 12 chapters and 8 appendices. It covers machine layout, design of the collider, the booster,  linac accelerator, the injector, design of the superconducting RF, RF power source, magnets, power supply, vacuum, and monitoring, control and mechanical systems. It also covers the cryogenic system, common facilities, civil engineering, radiation protection, and the option of upgrading to a Super proton-proton Collider (SppC). Alternative options for CEPC accelerator and opportunities for polarization at Z-pole are discussed in the appendices.

The CEPC Accelerator CDR can be found at https://arXiv.org (document 1809.00285) or at the official CEPC website: http://cepc.ihep.ac.cn/CDR_v6_201808s.pdf.