Surface studies of contaminants generated during electropolishing

Electropolishing is now the preferred method for chemical treatment of niobium cavities. It provides a very smooth surface and, after baking, accelerating fields between 35-40 MV/m . However, the reproducibility of performance needs to be improved substantially. Some of the leading causes are related to contaminant residues after electropolishing, such as sulfur particles. We have carried out studies to enhance the deposition of such particles so that we can isolate and study the residues. We will present analysis of these studies using optical microscopy and SEM. In an attempt to dissolve these contaminants, we have also conducted studies on the effectiveness of various rinsing agents, such as degreasing agents and dilute HF.