Fringe field interference effects on field quality for quadrupole magnets

A study of fringe field interference effects on field quality of quadrupole magnets for a newly developed superconducting proton cyclotron beamline was presented in this paper. The integral field gradient homogeneity was better than ± 5 × 10E-4 without fringe field interference. The influence of fringe field interference on field quality and integral field degradation was analyzed with 3D simulations. The results showed that the field quality was not affected when only yoke interference was considered. Besides, the characteristics of field quality with current interference were also studied. The integral field degradation and multipole field components were analyzed to research the variation of field quality. It showed that the inhomogeneity of integral field degradation at different beam orbits was the main disturbance for integral field quality. Finally, a normalized formula of the integral field degradation with different parameters was established, which will be the data reference for the newly developed superconducting proton cyclotron beam line assembly in the near future.