Speaker
Description
The performance of Superconducting Radio Frequency (SRF) cavities is critically dependent on surface quality. While Electropolishing (EP) has traditionally been the standard for achieving low-roughness surfaces on Niobium (Nb) and Copper (Cu) substrates, it relies on hazardous and corrosive acids. Since 2019, Legnaro National Laboratories (LNL) has developed an eco-friendly alternative: Plasma Electrolytic Polishing (PEP). Utilizing only diluted salt solutions, PEP offers significant advantages over EP, including superior removal rates ($2\text{-}8~\mu\text{m/min}$ for Nb and $3\text{-}30~\mu\text{m/min}$ for Cu) and surface roughness ($R_a$) below tens of nanometers. Furthermore, the setup has been optimized to use external cathodes, eliminating the need for complex internal cathode insertion in elliptical cavities. Following the establishment of patented recipes in 2022, PEP was successfully applied to Cu $6~\text{GHz}$ elliptical cavities, QPRs, and 3D-printed devices. A major milestone was achieved in August 2024 with the successful scaling of the process to a $1.3~\text{GHz}$ Cu elliptical cavity. In collaboration with CERN and KEK, the RF performance of PEP was validated on a hydroformed seamless cavity (coated with Nb thin film), demonstrating compatibility and slight performance improvements over standard EP. Further RF validation of PEP on differently produced Cu 1.3 GHz cavities will be presented.
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