• M. Nishiwaki, H. Hayano, S. Kato, T. Saeki, M. Sawabe.
  KEK, Ibaraki
• T. Noguchi
  KAKEN Inc., Mito
• P.V. Tyagi
  Sokendai, Ibaraki

In order to achieve higher and more stable performance of super conducting radio-frequency (SRF) cavities, extensive effort in development and application has been done for surface treatment and conditioning methods. Those methods have been evaluated with vertical tests showing lots of remarkable results in cavity performance. However it cannot be well understood yet how surface treatment or conditioning contributed to the results and which step of process in the treatment or conditioning affected the results. In this article, we describe our try to understand those questions focusing on the surface analyses with scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) for electro-polishing (EP) processed niobium sample coupons.