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TY - CONF AU - Reece, C.E. ED - Michel, Peter ED - Arnold, André ED - Schaa, Volker RW TI - An Experimental Analysis of Effective EP Parameters for Low-Frequency Cylindrical Nb Cavities J2 - Proc. of SRF2019, Dresden, Germany, 30 June-05 July 2019 CY - Dresden, Germany T2 - International Conference on RF Superconductivity T3 - 19 LA - english AB - While the basic process of electropolishing niobium with 1:9 HF:H₂SO₄ electrolyte has been well characterized, the specific process parameters used to electropolish different superconducting radio frequency (SRF) cavity geometries requires thoughtful attention. One seeks to realize confidently local diffusion-limited polishing at each point on the surface while maximizing uniformity of removal rate. Since the reaction rate is temperature dependent, this implies that one must manage the cavity surface temperature during polishing. Too-high applied voltage aggravates temperature and thus removal non-uniformity, but too-low applied voltage risks placing the large-diameter locations "off the current plateau," yielding etching rather than polishing. The majority of recent experience has been with elliptical L-band SRF cavities and some half-wave cavities at ANL. Lower frequency cavities with increased surface area and larger cathode-to-equator distance require fresh analysis and optimization. In preparation for SNS PPU project, JLab performed some EP process development runs with SNS high beta cavities to help identify viable parameter regimes for communication to cavity vendors. Results from this study are presented. PB - JACoW Publishing CP - Geneva, Switzerland SP - 472 EP - 476 KW - cavity KW - cathode KW - SRF KW - niobium KW - polarization DA - 2019/08 PY - 2019 SN - "" SN - 978-3-95450-211-0 DO - doi:10.18429/JACoW-SRF2019-TUP029 UR - http://jacow.org/srf2019/papers/tup029.pdf ER -