Study of the effect of electro polishing on intentional surface defects like pyramidal dents, pits on niobium samples

Electro-polishing (EP) of Superconducting radio frequency (SRF) cavities is considered as a major surface treatment process. EP helps in removal of damaged layer, dissolution of surface contamination and provide smooth finish for the RF surface. However, even after proper control of EP parameters, the SRF cavities have been found to quench abruptly due to the presence of defects such as dents, pits and other topographical defects. Hence, it is necessary to understand the response of various types of defects to the standard EP procedure. In this work, Niobium (Nb) sample was prepared with artificial dents and pits, which were subsequently electropolished in stages. The changes in the 3D topography of the defects are reported at various intervals of EP. (author)