Niobium surface modification in a microwave discharge

Surface preparation techniques for Niobium superconducting RF cavities commonly employ chemical or electrochemical polishing. With wet chemical polishing and the final dry air treatment, the formation of a non-superconductive Niobium oxide layer is unavoidable since oxidation starts as soon as the chemical process stops. For that reason a dry surface modification is highly desirable. Plasma etching may provide a unique opportunity to explore oxide-free surfaces by directly testing a cavity surface after processing without exposure to air. We studied the effects of a cavity microwave discharge in Ar and Ar-Cl$_{2}$ mixtures on removal of oxide layer of an electrically biased Niobium samples. Results on discharge characterization during the process will be presented at the conference.