Beam Simulation for Improved Operation of Cyclotron NIRS-930

A beam inside NIRS-930 cyclotron (Thomson-CSF, Kb=110 MeV, Kf=90 MeV) is diagnosed by such device as differential prove and phase prove, though the beam behavior is not well recognized. To understand the behavior of the beam, beam simulation is an effective method. The SNOP code is developed to simulate multiple particles in a cyclotron taking account of space charge effect using PIC method. Firstly, comparing the simulation results with actual measurement, we can ensure the correctness of simulation. The phase variation of 18 MeV proton beam of simulation was compared to that of the experiment. Both results show similar tendency. The beam loss point was also studied in simulation changing beam injected phase. We found that a lot of particles injected with early phase are lost at deflector. On the other hand, a lot of particles injected delayed phase is lost at inflector. The difference of the phase of maximum transmission ratio at inflector and deflector was 20°. Furthermore, space charge effect was found to decrease transmission efficiency if the injection beam current is more than ~1 mA. Considering the results of the simulation, actual operation of the NIRS-930 cyclotron can be improved.