He, T.L. Bai, Z.H. Li, W.W. Xu, H. JACoW Publishing Geneva, Switzerland 978-3-95450-265-3 10.18429/JACoW-SAP2023-MOPB010 English 30-33 impedance vacuum ECR storage-ring coupling Contribution to a conference proceedings 2024 2024-11 https://doi.org/10.18429/JACoW-SAP2023-MOPB010 https://jacow.org/sap2023/papers/mopb010.pdf In diffraction-limited storage rings, non-evaporable getter (NEG) coatings are generally used to assure the ultrahigh vacuum, which, however, also increase the beam coupling impedance that can affect beam dynamics. Ignoring the influence of coating roughness, the impact of NEG coatings on the impedance mainly depends on the coating thickness and resistivity. In this paper, we investigate the impedance characteristics of a round CuCrZr vacuum chamber coated by NEG with different thickness and resistivity.