In-Situ SRF Cavity Coating And Cleaning For Defect-Free Conformal Niobium Films

Superconducting materials are essential for particle accelerators to support high-energy physics research. New manufacturing processing techniques are needed to enable next generation niobium- based SRF cavities that reduce cost, improve quality factor, increase accelerating gradient, and provide in-situ cleaning to mitigate field emission. The high-power impulse magnetron sputtering (HiPIMS) technique has received growing interest to deposit thin-films of high-quality materials at low temperature. A recent HiPIMS innovation using a positive polarity reversal has been shown to control ion energy to selectively grow films with preferred grain orientation, high-density and tailored electro-optical properties. This technique has application for conformal coating of non-planar objects with precision and it can be used for multilayer structures. The technical approach is to evaluate using the innovative HiPIMS positive polarity reversal technique for sputtering advanced niobium films for SRF cavities (i.e. Nb, NbN, NbTi, Nb3Sn, etc.), as well as the ability to etch clean surfaces to mitigate field emission and multipactoring for high-Q cavity structures. Proof of concept feasibility will be demonstrated in a lab environment paving the way for Phase II implementation readiness.The HiPIMS technology will enable lower cost accelerators, decreased power consumption, reduced size and higher efficiency with increased safety margin for operation without sparking. The technique will also support industrial accelerators (operating at RF frequencies of e.g. 600-700 MHz) in order to provide low cost, reliability and long-term stable operation. The SBIR program will also support emerging small businesses and job creation in the Midwest.