Magnetic Field Simulation and Harmonic Analysis of CSNS/RCS Quadrupole Prototypes

In the rapid cycling synchrotron of China Spallation Neutron Source (CSNS/RCS), the 48 quadrupole magnets are divided into four types according to their apertures. Four types of quadrupole prototype magnets were manufactured and measured using a harmonic coil system. The first magnetic field measurement results at DC current show that some multipole magnetic field contents are larger than those of the requirement and should be reduced. The magnetic field harmonic adjustment scheme was determined and carried out based on the 3D magnetic field simulation with OPERA. After the correction, all the magnetic harmonics of the quadrupole prototype magnets are within the requirements.