Development of Curved Combined-Function Superconducting Magnets for a Heavy-Ion Rotating-Gantry

Combined-function superconducting magnets are designed for a heavy-ion rotating gantry. The superconducting coils of these magnets have a surface winding coil structure. To minimize sagitta, the superconducting magnets as well as their coils have a curved shape. Ten superconducting magnets are installed on the rotating gantry. With the superconducting magnets, the rotating gantry can transport carbon ions having 430 MeV/u to a patient with irradiation angles of over ±180 degrees, and is further capable of performing three-dimensional raster-scanning irradiation. Since the superconducting magnets would be rotated by ±180 degrees, compact cryocoolers are employed for cooling of the superconducting coil. Because the coil has quadrupole and dipole layers, the superconducting magnets can provide both quadrupole and dipole magnetic field. Using the combined-function superconducting magnets, we can design a compact rotating gantry, while keeping a large scan size at the isocenter; the length and the radius of the gantry would be approximately 13 and 5.5 m, respectively, which are comparable to those for the existing proton gantries. In this paper, we report the design of the superconducting magnets as well as results of some tests.