Minimal surface roughness is a critical feature for high-fieldsuperconducting radio frequency (SRF) cavities used to engineerparticle accelerators. Current methods for polishing Niobiumcavities typically utilize solutions containing a mixture ofconcentrated sulfuric and hydrofluoric acid. Polishing processessuch as these are effective, yet there are many hazards and costsassociated with the use (and safe disposal) of the concentrated acidsolutions. An alternative method for electrochemical polishing ofthe cavities was explored using a novel ionic liquid solutioncontaining choline chloride. Potentiostatic electrochemicalimpedance spectroscopy (EIS) was used to analyze the ionicpolishing solution. Final surface roughness of the Nb was found tobe comparable to that of the acid-polishing method, as assessed byatomic force microscopy (AFM). This indicates that ionic liquidbasedelectrochemical polishing of Nb is a viable replacement foracid-based methods for preparation of SRF cavities.
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