Fastest electropolishing technique on niobium for particle accelerators

As niobium (Nb) based superconducting radio frequency (SRF) technology is maturing, more and more particle accelerators go superconducting. One of the most important challenges that SRF community is facing is how to reduce the production cost and increase throughput of Nb SRF cavities. R&D in this field has demonstrated that the inner surface smoothness of a Nb cavity is one of the key issues in this regard. Nb SRF cavities with a smoother surface finish tend to have fewer field emission limited RF tests and a better chance to reach a high accelerating gradient. Previous experiments have demonstrated that buffered electropolishing (BEP) could produce the smoothest surface finish ever reported in the literature. In this paper, it is showed that under suitable experimental conditions, Nb removal rate can reach as high as 10 μm/min. The mechanism responsible for high Nb removal rate during BEP treatments as well as the implications of BEP technique for cost savings in the fabrication of Nb SRF cavities will be discussed. Copyright © 2011 by IPAC'11/EPS-AG.