Fabrication of a Model Magnet Using Coated Conductors for FFAG Accelerators

A project to develop fundamental technologies for accelerator magnets using high-Tc superconductors (HTSs) was carried out from FY 2009 to 2018 and funded by the Japan Science and Technology Agency under its S-Innovation Program. In this research program, conceptual design studies of fixed—field alternating gradient (FFAG) accelerators for carbon cancer therapy were carried out. In the conceptual magnet design for a full-scale, spiral-sector FFAG accelerator, a rare earth elementbased REBa2Cu3Ox (REBCO) superconducting coated conductor was incorporated to realize a compact, high-field magnet. With the aim of demonstrating the winding technique of REBCO coils that meet the requirements of the FFAG accelerator, we developed a cryocooler-cooled, reduced-size test magnet incorporating multiple REBCO coils, referred to here as the "model magnet". All coils of the model magnet were designed to have a part with a negative-bend shape, and the coils close to the beam duct were designed to have a three-dimensional winding shape. This paper describes the design and fabrication of the model magnet.