Liu, X. Chen, Q.S. Chen, W. Liang, Z.K. Liu, K.F. Qin, B. JACoW Geneva, Switzerland 978-3-95450-167-0 10.18429/JACoW-Cyclotrons2016-MODM04 English 42-44 MODM04 proton simulation cyclotron dipole target Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-Cyclotrons2016-MODM04 http://jacow.org/cyclotrons2016/papers/modm04.pdf For implementation of proton therapy, Huazhong University of Science and Technology has planned to construct a 250 MeV/500 nA superconducting cyclotron for proton therapy. In the beam-line, the scanning system spreads out the proton beam on the target according to the complex tumor shape by two magnets for horizontal and vertical scanning independently. As dipole magnets are excited by alternating currents and the maximum repetition rate is up to 100 Hz, the eddy currents are expected to be large. This paper introduces the design of these two scanning magnets and analyzes the eddy current effect. Slits in the end pole are proven to be an effective way to reduce the eddy current. Different directions, distributions and width sizes of slits are simulated and compared to determine the slits arrangement. At last, the maximum temperature of the optimized scanning magnets reaches the temperature requirements.