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Analysis of Pulse-Reverse Nb Electropolishing with  H2so­­4 for Srf Cavities

Wednesday, 1 June 2016: 11:45
Cobalt 520 (Hilton San Diego Bayfront)
H. Tian, C. E. Reece (Jefferson national lab), M. Meyerson (University of Maryland), and C. McCord (University of West Florida)
The performance of superconducting radiofrequency (SRF) cavities is greatly affected by the topography of the interior surface, so it is imperative that the surface be clean metal as smooth as possible. Currently, the 1:10 volume ratio HF (49%) and H2SO4 (96%) electrolyte was widely used for high field SRF cavity production, the problem with using HF is that it is dangerous both to people and to the environment.  A new method that has been developed to smooth the surface is pulse reverse electropolishing (EP). This method uses aqueous H2SO­­4 as the electrolyte and alternating anodic and cathodic pulses to oxidize the niobium (Nb) and then remove the oxide from the surface [1]. Previous studies have shown that pulse reverse EP effectively polishes the surface of Nb SRF cavities [1,2].. In order to better understand polishing mechanism and optimize the operating parameter for cavity production, systematic electrochemical experiments have been carried out to further explore the oxide removal process, the effect of positive and negative pulse duration, pulse structure, off time between positive and negative pulses, concentration of H2SO­­4, and determine optimum polishing parameters for reliable Nb SRF cavity production process, the results will be reported.