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 $\sim$ 70 km. The required dipole field strength is 20 T for SppC. As the start of a long-term R&D plan for high-field accelerator magnet technology at IHEP, a 15-T short sample field $\hbox{Nb}_{3}\hbox{Sn}$ 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 field uniformity will be reached at a reference radius of 15 mm. Magnetic analytical modeling and FEM cross section study of this high-field 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 $J_{\rm c}$ level of $\hbox{Nb}_{3}\hbox{Sn}$ and HTS superconductors.

I. Introduction

IHEP (Beijing, China) is proposing to build a two-stage circular particle collider in the near future [1]. The first stage CEPC will be capable of providing 240–250 GeV center-of-mass energy for electrons and positrons. The second stage SppC will provide 70–100 TeV center-of-mass energy for protons. The circumference of the accelerator for CEPC and SppC will be in the range of 50 to 70 km. The required dipole field strength for SppC is 20 T. As part of the R&D effort for CEPC-SPPC, IHEP has organized a team to start the development of high field accelerator magnet technology in China. The objective is to build and test a 20 T dipole magnet before 2030.