Investigation of spin rotators in CEPC at the Z-pole

Abstract

Abstract Purpose Longitudinal polarization is an important design aspect of the future 100 km-scale Circular Electron Position Collider (CEPC). Spin rotators are needed in the CEPC collider rings to make the beam polarization along the longitudinal direction at the interaction points (IPs). This paper focuses on the design of spin rotators for CEPC at the Z-pole (45.6 GeV). Methods The design of spin rotators in the CEPC at the Z-pole is based on solenoid magnets and horizontal bending magnets sections. The coupling of transverse motion introduced by solenoids is compensated with quadrupole lenses. Adjustments have been made to the layout to implement the spin rotators into the collider rings. Results Longitudinal polarized beam can be achieved at the IPs with the spin rotators. High degree of polarization is attainable, while the effect of spin rotators on orbital motion is acceptable. The detailed simulation results will be presented. Conclusion A solenoid-based spin rotator configuration is designed and integrated into the CEPC collider ring lattice. According to the simulation results, the polarization requirements can be satisfied.