Li, J.Q. Chen, Q.S. Fan, K. Tang, K. Tian, P. JACoW Publishing Geneva, Switzerland 2673-5350 978-3-95450-204-2 10.18429/JACoW-IBIC2019-WEPP010 English 530-533 WEPP010 cavity proton coupling simulation impedance Contribution to a conference proceedings 2019 2019-11 https://doi.org/10.18429/JACoW-IBIC2019-WEPP010 http://jacow.org/ibic2019/papers/wepp010.pdf In proton therapy facility, non-destructive beam diagnostic devices are essential for on-line measurement during the patient treatment. To meet the clinical requirement, the beam current becomes ultra-low of the order of nano-ampere, which is a great challenge to non-destructive beam diagnostics because of the extremely low signal level. Compared with conventional non-destructive beam diagnostic devices, the cavity beam position monitor (BPM) has a high shunt impedance to get enough power levels, so a cavity BPM system is designed for HUST-PTF. It is made up of two resonant cavities called reference cavity and position cavity, respectively. Both cavities are simulated and optimized by CST Microwave Studio and Particle Studio. Finally, the electronics of cavity BPM we plan to use is shown.