Fabrication and Experiments on a 1/2-Scale Demonstration NI-REBCO Coil System of a Skeleton Cyclotron for Cancer Therapy

We have been developing a high-temperature superconducting skeleton cyclotron (HTS-SC) as an ultra-compact and high-intensity accelerator that can produce an alpha-ray emitting radioisotope (At-211) for targeted alpha-particle therapy, which is expected to be effective in treating advanced cancer. In addition, multiple air-core REBCO coils without an iron core allow variable output energy. Furthermore, a new coil technology integrating 5-High basic technologies (high field, high field accuracy, high mechanical strength, high thermal stability, and high current density) will be applied to the REBCO coil system for the HTS-SC. As a preliminary step, a REBCO coil system for an ultra-baby-skeleton-cyclotron (UBSC), which is a 1/2-scale demonstration model, was fabricated to evaluate magnetic field accuracy, coil deformation during cooling and excitation, and thermal stability of the HTS-SC. The Yoroi coil structure was adopted for the UBSC for high mechanical strength and a no-insulation (NI) coil winding technology for both high thermal stability and high current density. In this paper, we report results on cooling and excitation tests using the 1/2-scale model NI-REBCO coil system.