Surface study of niobium samples used in superconducting rf cavity production

We have initiated an effort to study the Nb/oxide interface and its effect on rf cavity performance. The oxide layer on processed cavity surfaces is dominantly Nb₂O₅, which has a high secondary electron yield that may be detrimental to cavity performance. Our effort focuses on developing new processes to remove the oxide layer by easily achievable means. In this presentation, we show some preliminary results of a surface study of the metal/oxide interfaces on Nb samples that have undergone different surface processes usually used in cavity production. The results suggest that Nb₂O₅ is not stable when subjected to heat treatment of ~250°C, and that it converts into monovalent or even subvalent oxides that are metallic in nature