Development of HTS magnets for separated sector cyclotrons

Usage of high energy and high intensity accelerators has been widely spread across industrial and medical fields. Accordingly, reliability and cost performance are vital factors for these applications. One of the most important features of cyclotron is its power efficiency. Utilizing high temperature superconductors (HTS) for magnets, a pinnacle of power efficient and stable high energy accelerator can be realized. Here, we propose a next generation cyclotron with HTS technology. As a first step, we are planning to develop an HTS cyclotron as an injector for K400 ring cyclotron at RCNP. It will be the first attempt in the world. This plan will improve beam intensity by factor of 10 in the existing facility. The most crucial challenge is the development of large-size HTS magnets that can be used in SSC. A one-meter-size HTS dipole magnet is designed and fabricated as a prototype. Evaluation for magnetic and thermal characteristics are carried out. As a result, excitation method to eliminate magnetic field drift due to flux creep is developed. The conceptual design of the SSC is completed under the demands of injecting beam to the ring cyclotron. Magnetic, thermal and mechanical analyses are performed to evaluate the integrity of the coil assembly of the magnet. Consequently, temperature margin is 32 K, and the critical current is 2.8 times of maximum current of excitation under the maximum field. Feasibility of the HTS injector cyclotron is confirmed. (author)