Speaker
Description
he performance of niobium cavities used in superconducting accelerators is strongly governed by the morphology, chemical state, hydrogen content, and defects of the outermost surface region into which the electromagnetic field penetrates. The standard hydrofluoric acid–sulfuric acid electropolishing process has several problems, including high operational hazards and toxicity, as well as hydrogen uptake during polishing, which can lead to hydride formation and degrade the accelerating performance of the cavity. To address these issues, the author developed an electropolishing process using an organic-solvent-based electrolyte that does not use hydrofluoric acid or an aqueous solution, and successfully achieved mirror finishing of niobium flat samples. In addition, suppression of hydrogen uptake was experimentally demonstrated using a separately developed low-water-content organic-solvent-based electrolyte system. Based on these results, the next step will be to proceed with electropolishing of 1.3 GHz single-cell cavities.