A Method to Improve the Field Quality of the Curved Canted–Cosine–Theta Dipole

A proton therapy equipment named SC200 is being developed in the Institute of Plasma Physics (IPP), Chinese Academy of Sciences (CAS) and Hefei CAS Ion Medical and Technical Devices Company, Ltd. In order to develop a lightweight gantry for proton therapy, the canted–cosine–theta (CCT) superconducting magnet was considered to apply in the superconducting gantry development. In this study, the magnetic field and harmonic components of the curved CCT dipole were analyzed. As the curved CCT coil is no longer symmetric, great high-order harmonics exist. An optimization method to improve the field quality of the curved CCT dipole was presented. A symmetry-curved CCT dipole, which was called an S-curved CCT dipole, was approached in this study. With the S-curved CCT, all the integral high-order harmonics can reach the requirement of 10
⁻⁴
. The design of the curved CCT dipole magnet with 2.67-T dipole field and 870-mm bending radius was introduced and analyzed in this study.