Author: GIOVANNI MONDIN ; Type of thesis: Bachelor Thesis
Abstract: At LNL (Legnaro National Laboratories) a new type of electrolyte for niobium electropolishing is being tested. It is an ionic liquid, i.e. a salt that is liquid at room temperature, obtained by mixing two solids: urea and choline chloride. This electrolyte was first introduced in 2003 by Abbot et al. Subsequently, they showed its potential by successfully electropolishing stainless steel. Recent studies at LNL have proven that electropolishing niobium, using the above ionic liquid, is possible. The results are very promising considering the fact that this is a new process, virtually unknown, unlike the “classic” electropolishing process in acid solution, which dates back to the 70s and has been widely studied and improved.
If an efficient and reproducible method for electropolishing niobium superconducting cavities with ionic liquid were developed, it would demonstrate the existence of a viable alternative to the use of sulfuric and hydrofluoric acid in the treatment of cavity surfaces. In particular, it would be possible to introduce large-scale use of a chemical compound decidedly less dangerous, less polluting and less expensive than those used today.
In this thesis the electropolishing process of small niobium samples in ionic liquid has been investigated, with the aim of providing guidance for future tests on cavity electropolishing. By exploring the basic parameters involved in the process (current density, temperature, duration, stirring), the optimum values in order to obtain the best possible polished surface have been determined. Once the best conditions have been found…