Search

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 (211At) for targeted α-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.

High temperature superconducting REBCO tape has the characteristic of maintaining high critical current density under strong external magnetic field, which makes it an ideal material for the construction of air-core electromagnets of accelerator and electron cyclotron resonance (ECR) ion source. In Research Center for Nuclear Physics, Osaka University, a non-insulated air-cored REBCO coil assembly has been constructed. This coil assebmly consists of three circular REBCO solenoid and six racetrack REBCO coil. This coil assembly will be used as an electromagnet of a multi-frequency ECR ion source, and is also developed as a key technology development of an air-core cyclotron. The magnetic field of this ion source are designed, and 77 K performance tests of the assembly are carried out in order to examine the capability of REBCO coils of inducing magnetic field under external field. In this work, the test results and the magnetic field designed for the ECR ion source will be presented and discussed.

We have introduced the Skeleton Cyclotron, a high-temperature superconducting (HTS) air-core compact cyclotron designed to produce medical radioisotopes (RIs) to be used in targeted alpha-particle therapy, an innovative approach to cancer treatment. The coil system of the Skeleton Cyclotron comprises circular main coils for creating an isochronous field and non-circular sector coils to generate an azimuthally varying field. All of these coils are wound using the REBCO tape with a no-insulation (NI) winding technique, chosen for its ability to provide high current densities and thermal stability. To demonstrate the feasibility of our concept, we developed a half-size prototype called the Ultra-Baby Cyclotron. This prototype includes three pairs of sector coils and four main split coils. To enhance the durability of the coils and protect them from the intense electromagnetic forces involved, we reinforced them with a YOROI-coil (Y-based Oxide superconductor and Reinforcing Outer Integrated coil) structure. In the summer of 2022, we started testing on the Ultra-Baby Cyclotron, and then we conducted measurements of mechanical deformations in the coils. Additionally, we conducted numerical simulations. This study presents the experimental and numerical results regarding the mechanical behaviors of NI-REBCO coils in the Ultra-Baby Cyclotron.