In proton therapy systems, the large size of equipment and facilities poses a challenge. Recently, superconducting technology has been applied to proton therapy accelerators for downsizing the facility. In this article, following an introduction to proton therapy and accelerators, commercially available superconducting accelerators and the superconducting cyclotron SC230 will be presented as a development example. The recent technological trends in proton therapy systems will also be discussed.

The National Institutes for Quantum Science and Technology （QST） is responsible for manufacturing 33 TF conductors and 9 TF coil winding packs （WP）. QST has been conducting these manufacturing processes. However, technical issues related to the interface between the TF conductor and WP arose due to differences in standards and quality culture among countries. These issues included PT indication on the welding line of the conductor jacket and high carbide concentration during heat treatment. QST could overcome these issues with the cooperation of manufacturers, domestic agencies, and the ITER organization. In addition, QST revealed the pressure drop characteristics of the conductor in the transverse and longitudinal directions, these data will prove valuable in future ITER operations. Based on this experience in TF conductor and WP manufacturing, a proposal for an optimized scheme for developing DEMO coils is described.

The National Institutes for Quantum Science and Technology （QST） have completed the manufacturing of nine ITER TF coils. In TF coil manufacturing technologies, insulation is one of the most critical techniques because insulation failure can directly lead to TF coil scrapping. Therefore, QST developed insulation techniques via trials and with the cooperation of manufacturers. In addition, COVID-19 has influenced impregnation work in WPs and coil case assemblies. Alternative resins with especially low viscosity were developed to overcome this difficulty. Finally, based on the experience of TF coil insulation, insulation failure in JT-60SA superconducting coils was repaired. As a result, the first plasma was achieved in October 2023.