Chouhan, V. Bice, D.J. Burk, D.A. Chandrasekaran, S.K. Cravatta, A.T. Dubiel, P.F. Eremeev, G.V. Furuta, F. Guilfoyle, B.M. Kelly, M.P. Melnychuk, O.S. Netepenko, A.V. Ng, M.K. Ozelis, J.P. Park, H. Reid, T. Ring, T.J. Wu, G. JACoW Publishing Geneva, Switzerland 2673-5504 978-3-95450-234-9 10.18429/JACoW-SRF2023-TUPTB042 English 512-516 cavity cathode SRF niobium polarization Contribution to a conference proceedings 2023 2023-09 https://doi.org/10.18429/JACoW-SRF2023-TUPTB042 https://jacow.org/srf2023/papers/tuptb042.pdf Electropolishing (EP) of 1.3 GHz niobium (Nb) superconducting RF cavities is conducted to achieve a desired smooth and contaminant-free surface that yields good RF performance. Achieving a smooth surface of a large-sized elliptical cavity with the standard EP conditions was found to be challenging. This work aimed to conduct a systematic parametric EP study to understand the effects of various EP parameters on the surface of 650 MHz cavities used in PIP-II linac. Parameters optimized in this study provided a smooth surface of the cavities. The electropolished cavities met the baseline requirement of field gradient and qualified for further surface treatment to improve the cavity quality factor.