Design of the Fast Scanning Magnets for SC200 Proton Therapy Facility

At the Institute of Plasma Physics of the Chinese Academy of Sciences, a design of the pencil beam scanning nozzle is being planned. The main goal of the design is to meet the requirements of the radiation field and the scanning speed of the superconducting accelerators SC200 and to achieve a compact structure. Scanning magnets are one of the core components in the pencil beam scanning system and used to control the trajectory of the proton beam to form a radiation field to be tumor shape. This paper mainly discusses the physical considerations and requirements of the scanning system and scanning electromagnetic design. The tapered air gap of scanning magnet Y was used to accommodate the deflection envelope of the scanning magnet X. Since the two scanning magnets are excited by alternating currents and the maximum repetition frequency are up to 50 Hz and 12.5 Hz, respectively, eddy currents and losses are expected to be significant. To study the eddy current effect, the eddy current and steady-state thermal simulation of the magnet end plate were carried out, and the results of the simulation were discussed.