Design of the Shift Bump Magnets for the Beam Injection of the 3-GeV RCS in J-PARC

The injection system of the 3-GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) consists of four main orbit bump magnets (shift bump) to merge the injection beam with the circulating beam. In order to control the injection beam with sufficient accuracy, the shift bump magnets need a wide uniform magnetic field. The magnetic field design and the structural analysis of the shift bump magnets have been performed using three-dimensional electromagnetic and mechanical analysis codes. The shift bump magnets have realized a uniform field with less than 0.35% inhomogeneity over a wider area, which is 400 mm in width and 240 mm in height. Furthermore, the magnets operate with a high magnetic field and they are located in high radioactive level area. The flexible bar is applied to the coil as the countermeasure for thermal expansion and the insulator has strong radiation resistance