Advanced Horizontal CVD Reactor Development for Increased Process Efficiency to Produce Seamless Thick-Film CVD Niobium-Lined Copper SRF Cavities

DOE is interested in innovative fabrication technologies for cost-effective high-Q, high-field superconducting radio frequency (SRF) cavities necessary for the economic viability of future accelerators and upgrades. Ultramet continues to develop transformative chemical vapor deposition (CVD)-based fabrication processes to reliably deposit high- quality superconducting thick-film and thin-film niobium possessing performance capabilities near or better than bulk niobium for application to the interior surface of less costly copper accelerator component structures such as cavities, complex couplers, and nosecones as an alternative to solid bulk niobium. The proposed effort to develop a horizontal CVD reactor, versus the conventional vertical CVD reactor designs, is a critical first step in scaling Ultramet’s CVD-based niobium-on-copper SRF accelerator component fabrication process necessary for implementation of the technology in the production of cost-effective, seamless high-gradient superconducting accelerator components. The new CVD reactor design will effectively increase cavity fabrication process efficiencies and reliability. Ultramet will develop a highly efficient horizontal CVD reactor needed to adapt advanced CVD processing techniques to the fabrication of thick-film CVD niobium-lined copper SRF cavities as a necessary first step for scaling Ultramet’s rapid CVD niobium process to accommodate the cost-effective fabrication of seamless multi-cell SRF cavities. This project will focus on constructing the new CVD reactor from preliminary designs to form a niobium coating on the interior surface of an existing single-cell copper cavity of the International Linear Collider (ILC) design at full scale.Success in this research will represent a significant technical milestone in developing reliable fabrication techniques for reproducible high-performance accelerator cavity structures and components of varied geometries offering substantial cavity-related fabrication cost reductions for numerous superconducting accelerator programs worldwide. Cost reductions afforded by the new reactor design and use of the CVD-based seamless cavity fabrication-related technologies developed in this research include substantially reduced need for costly electron beam welding, elimination of the need for high-cost, high-purity starting materials, fewer processing steps, and robust niobium surface layers compatible with conventional bulk niobium cavity surface conditioning methods.