Zhu, J.Y. Li, X. Lu, Z.J. Yu, J.B. JACoW Publishing Geneva, Switzerland 2673-7035 978-3-95450-224-0 10.18429/JACoW-FLS2023-WE4P33 English 207-210 cavity HOM impedance damping photon Contribution to a conference proceedings 2024 2024-01 https://doi.org/10.18429/JACoW-FLS2023-WE4P33 http://jacow.org/fls2023/papers/we4p33.pdf The Southern Advanced Photon Source (SAPS) aims to achieve ultra-low emittances and is expected to adopt low-frequency cavities (< 200 MHz) to accommodates on-axis injection. This paper focuses on the design of a 166.6 MHz HOM-damped normal conducting (NC) cavity for the SAPS. We propose a novel approach to achieve efficient HOM damping by optimizing the lowest frequency HOM and implementing a beam-line absorber in a coaxial resonant NC cavity. Notably, unlike beam-line absorbers for conventional NC cavities, the presence of a large beam tube in a coaxial resonant cavity does not affect the accelerating performance. This enables effective HOM damping while maintaining a high shunt impedance in a NC cavity. The numerical simulation results show that a compact copper cavity with effective HOM damping and excellent RF properties has been achieved.