Liu, X.Y. Fang, P.Z. Li, Y. Wang, X.W. Wang, Z.J. Wang, Z.M. Xiong, Y. Yao, H.J. Zheng, S.X. JACoW Publishing Geneva, Switzerland 978-3-95450-265-3 10.18429/JACoW-SAP2023-TUPB006 English 92-95 resonance synchrotron space-charge injection simulation Contribution to a conference proceedings 2024 2024-11 https://doi.org/10.18429/JACoW-SAP2023-TUPB006 https://jacow.org/sap2023/papers/tupb006.pdf Xi’an Proton Application Facility (XiPAF) has been operational since 2020, which can accumulate 2e11 protons after injection and 1e11 protons after acceleration. In this paper, we have investigated the XiPAF synchrotron nonlinearity by simulation and experiments, the beam loss occurs with resonance vx+2vy=5 in the absence of space charge, and resonance 2vx-2vy=0 in the presence of space charge. The stripping foil also plays an important role due to its multiple scattering effect and ionization energy loss effect.