The superconducting radio frequency (SRF) cavities are being used worldwide in particle accelerators to achieve a high energy beam of charged particles. These cavities are made of high purity niobium (Nb) material and work at 2 K temperature. The inner surface of these cavities plays the most important role in order to obtain good performances in terms of the high field gradient. Therefore, the surface treatments associated with SRF cavities are the key issues toward the achievement of the high field gradient larger than 35 MV/m during vertical test of the nine-cell cavity for International...