Magnetic Field Optimization and Tolerance Study of a Medical Superconducting Cyclotron

SC200 cyclotron is a compact superconducting cyclotron for proton therapy developed by the ASIPP (Hefei, China)-JINR (Dubna, Russia) collaboration. In this paper, some beam dynamics simulations are done to evaluate the magnetic field of SC200 measured by mapping system. Magnetic field is optimized by shimming bars and coils to make sure beam can be accelerated to the entrance of extraction system. The optimization of isochronism of magnetic field, beam radial oscillation caused by imperfect first harmonic of magnetic field, magnetic vertical focusing force and radial magnetic field at median plane are presented. The tolerance of imperfect average magnetic field bump and radial magnetic field are studied by beam dynamics simulation.