Design and optimization of scanning magnets for HUST-PTF.

We report scanning magnets manufactured at the Huazhong University of Science and Technology Proton Therapy Facility for use in pencil-beam nozzles in a fixed beamline. Such nozzles allow us to control the trajectory of proton beams to form the requisite radiation field for tumor therapy. Two AC-excited scanning magnets operate at a maximum frequency of 100 and 50 Hz, respectively, generating significant eddy currents that raise the temperature. We use transient electromagnetic analysis and thermal analysis to study the eddy current effect and control the temperature. In this paper, the maximum temperature rise of the scanning magnets is taken as the criterion to find the appropriate depth, shape, and distribution of slits. After the slits are optimized, the temperature rise of the scanning magnet is significantly reduced. Finally, the results of DC performance tests satisfy the requirements of the magnetic field.