Barrier Coating Development for Manufacture of Superconducting Radio Frequency Accelerator Cavities

In previous work for DOE, Ultramet has developed an advanced chemical vapor deposition (CVD) process for the consistent production of cavity-grade superconducting niobium, which has application in the manufacture of seamless bulk niobium cavities and ancillary components for use in the majority of superconducting particle accelerator systems in operation worldwide. An immediate critical need exists to develop economical barrier coating formation techniques on low-cost mandrels to enable the application of the newly developed CVD niobium process. The proposed project will lower the base fabrication costs of the evolving seamless component fabrication methodologies needed for the mass production of high- gradient superconducting particle accelerator components. Cost-effective diffusion barrier techniques that prevent the ingress of performance-compromising mandrel-borne contaminants such as carbon into the CVD niobium cavity material during fabrication will be investigated. The efficacy of the barrier coatings will be determined by measuring the RRR purity level and critical temperature of the final CVD niobium test specimens produced. Characterization, including RRR testing, will be performed by Cornell Universitys SRF Group. Commercial Applications and Other Benefits: Ultramets seamless CVD niobium SRF cavity fabrication process is uniquely well-suited for the near- net-shape fabrication of complex accelerator component geometries that are difficult or impossible to form by conventional hydro- and spin-forming methods. The proposed barrier coating development has excellent potential to substantially reduce the cost of fabricating high-performance accelerator components and minimizing the need for electron beam weld attachment.