Progress on Fluorine-free Electropolishing – Vlada Pastushenko – TFSRF-2014

Title: Progress on Fluorine-free Electropolishing
Author: Vlada Pastushenko
Institution: INFN-LNL
Abstract: High purity niobium (Nb) is used to make superconducting radio frequency (SRF) cavities. To improve the cavity performance it is necessary to reduce the surface resistance as much as possible. To achieve this goal each Nb cavity undergoes to a series of successive treatments (mechanical polishing, buffered chemical polishing, electropolishing, annealing). Choline Chloride-based ionic liquids are considered as a new class of electrolytes. Comparing to traditional ionic liquids, choline chloride-based ionic liquids are low toxic, biodegradable, and the price is generally low, which make them more and more attractive in green chemistry and industrial chemistry. Since it was found that, the mixture of Choline Chloride and Urea can polish Niobium every year, this solution has been improved. Was investigated the optimal ratio of Choline Chloride and Urea, studied the effect of additives, temperature and current density. When it was found suitable parameters for the polishing of planar samples, we have started to implement it to the polishing of 6 GHz Niobium cavities.