Chouhan, V. Hayano, H. Ida, Y.I. Ishimi, K. Kato, S. Monjushiro, H. Nii, K.N. Saeki, T. Sawabe, M. Yamaguchi, T.Y. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-THBA02 English 1024-1030 THBA02 cavity cathode experiment ion SRF Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-THBA02 http://srf2015.vrws.de/papers/thba02.pdf Horizontal electropolishing (HEP) is being used for final surface treatment of niobium SRF cavities. However a HEP system is equipped with complicated mechanism that makes it expensive and enhances cost of surface treatment of cavities especially when mass production is considered. Vertical electropolishing (VEP) has been introduced by other labs and the research is being carried out to establish the VEP technique. The VEP system requires simple mechanism and has advantages over HEP setup. Positive results have been obtained from the VEPed cavities also as shown by other labs. However further improvement in a VEP setup, cathode and VEP parameters is required. Marui Galvanizing Co., Ltd in collaboration with KEK has been working for development of VEP system, optimization of cathode and VEP parameters to obtain uniform Nb removal with a smooth surface of a cavity. Here we report our recent development of VEP system, unique Ninja cathode and parameter optimization with a 1-cell coupon cavity containing 6 Nb disk coupons at the beam pipes, irises and equator. The coupon surfaces were analyzed to obtain detail of the cavity surface.