Design of MgB2 Superconducting Bending Magnet for Beam Transport System of Particle Beam Therapy

A lightweight, active-shield-type superconducting magnet with high quench resistance has been developed using MgB₂ wire, intended for application as a bending magnet in the beam transport system of particle beam therapy equipment. To realize this, a novel coil configuration was devised, combining a saddle-type coil and a racetrack coil—an uncommon design approach. Fundamental magnetic field specifications and key performance metrics of the magnet were investigated. Particular focus was placed on determining the wire specifications required to minimize the number of power supplies for the magnetic field sweeps demanded in particle therapy systems. In addition, AC losses due to magnetic field sweeps were quantitatively analyzed, and the number of required cryocoolers was estimated based on both these losses and other heat ingress sources. While further optimization of MgB₂ wire properties remains necessary, the feasibility of applying this magnet design to clinical bending magnets has been successfully demonstrated.