Transient Simulation and Field Measurement of the Trim Quadrupoles and AC Sextupoles for CSNS/RCS Upgrade

In September 2018, China Spallation Neutron Source (CSNS) passed the national acceptance and started stable operation. Many scientific achievements have been made, but more and more experiments require accelerators with higher beam quality. Based on the current lattice layout and further research, an alternative upgrade plan is proposed for the CSNS, i.e., CSNS-II. The trim quadrupole magnet and the AC sextupole magnet are necessary. Both types of magnets with the number of 16 are respectively powered by the AC power supply and they were developed firstly in 2021. This article introduces dynamic magnetic field simulation, fringe field interference analysis, and DC/AC magnetic field measurements of the two types of magnets.