Design of Superconducting Magnets for a Compact Carbon Gantry

For widespread use of rotating gantries for carbon radiotherapy, we designed a new compact gantry. This new gantry consists of three combined-function superconducting magnets having a bending angle of 90°. The dipole field of the superconducting magnets is set to be B
_max
= 5.02 T, corresponding to a bending radius of 1.32 m for transporting carbon ions having kinetic energy of 430 MeV/u. The superconducting magnet also has three independent superconducting quadrupole coils, which are to be wound inside the dipole coil for beam focusing. The dipole and quadrupole coils are electrically isolated in the magnet and connected to independent power supplies so that each field component can be independently excited. Having used the combined-function superconducting magnets, the size of the rotating gantry would become very compact; the length and radius are 5.1 and 4.0 m, respectively. The magnetic field distributions of the superconducting magnets were calculated with a 3-D electromagnetic field solver, Opera-3d code. With calculated fields, the superconducting coils were designed to obtain uniform field distributions. In this paper, the design of this compact rotating gantry and the superconducting magnets is presented.