Magnetic Design Study of the High-Field Common-Coil Dipole Magnet for High-Energy Accelerators

The Institute of High Energy Physics (IHEP, Beijing, China) is proposing a two-stage particle collider: CEPC-SppC. The first stage is a circular electron-positron collider (CEPC), expected to carry out high-precision studies on Higgs bosons. Upon completion of the CEPC experiment, it will be upgraded to a super proton-proton collider (SppC), aiming at the discovery of physics beyond the standard model. The circumference of the accelerator for CEPC and SppC will be 50 ~ 70 km. The required dipole held strength is 20 T for SppC. As the start of a long-term R&D plan for high-held accelerator magnet technology at IHEP, a 15-T short sample held Nb₃Sn dipole is planned to be developed within the next five years. The common-coil configuration is adopted to provide space for two apertures with a maximum diameter of 60 mm. The 10^-4 level held uniformity will be reached at a reference radius of 15 mm. Magnetic analytical modeling and FEM cross section study of this high-held common-coil dipole has been done and will be presented here. A preliminary cross section study of the 20-T common-coil dipole will also be introduced; the design is based on the current J_c level of Nb₃Sn and HTS superconductors.