The magnet design study for the FFAG accelerator

The required magnetic field for the fixed field alternating gradient (FFAG) accelerator is proportional to the k-th power of the orbit radius where k is the field index of the accelerator. Although the field is constant in time, the design of the magnets is more difficult than that of the conventional synchrotron due to the intrinsically nonlinear field. There are several ways to design the FFAG magnet. The "iron pole shape" makes the field by changing the pole gap size along the radius, which is the most conventional and suitable for the compact FFAG. Another way is a "pole face winding" where the field is produced by distributing the coil current along the radius. Although it is a challenging design, a large and high field FFAG is feasible. The third one is a "multipole combination" in which the magnetic field is generated by combining the multipole components of the fields. This could be applied to superconducting magnets. The FFAG has the potential for various applications, and the magnet design of the FFAG should be selected properly for each application.