Speaker
Description
SRF R&D activities at INFN LNL cover all the cavity production chain with the main goal of producing the first prototype of a Nb3Sn on Cu 1.3 GHz elliptical cavity by the end of 2025. In particular INFN is focusing on Cu surface preparation by Plasma Electrolytic Polishing (PEP) and Nb3Sn coatings by DC Magnetron Sputtering.
Cu surface preparation by PEP presents several advantages over traditional EP, including a superior removal rate up to 30 μm/min and a final surface roughness (Ra) lower than tens of nm. The process scaling to 1.3 GHz Cu elliptical cavity has been done successfully in 2024 and a collaboration with CERN and KEK is ongoing to validate the RF performances of PEP on a hydroformed seamless cavity produced by KEK and coated with a Nb thin film at CERN. First results are presented in this talk.
An optimized recipe for Nb3Sn on Cu films deposited via DCMS was first established on small flat samples and then validated on bulk Nb by measuring the RF properties on a QPR sample. A Tc>17 K and a surface resistance of 25 nΩ at 4.5 K, 20 mT, 417 MHz, was measured, which is about 5 times larger than the baseline specifications for the LHC Nb/Cu cavities, and already fulfills the requirements for the FCC-ee. Finally, the scalability of the coating recipe from small flat samples to an elliptical cavity prototype is also discussed.
