Rapid Low Cost Fabrication for SRF Cavity and Associated Components

The US Department of Energy (DOE) Office of High Energy Physics (HEP) in collaboration with the US National Laboratories is engaged in an ongoing R&D program to develop Superconducting Radio Frequency (SRF) cavities for assembly into CryoModules (CMs) with higher accelerating gradients (Eacc) and higher Q’s, while simultaneously lowering fabrication costs. State of the art SRF cavities manufactured from bulk Nb sheet have reached a level of technology maturity where medium and large‐scale projects in High Energy and Nuclear Physics can be realized. While the performance of these bulk Nb cavities has reached a plateau, the costs of the raw Nb material has not, increasing 300% in the past decade. Revolutionary not evolutionary techniques are needed to dramatically reduce both materials and fabrication costs. One approach to reducing SRF cavity materials costs has been to replace the expensive bulk Nb (∼$300/lb.) cavities with an Nb thin films deposited on a less expensive bulk material such as Cu (∼$3/lb.). Advances in thin film deposition techniques leading to lower defects of Nb films offer great promise for improved performance compared with earlier Nb film coated cavities such as those used in LEP. Alternate thin film coatings such as Nb3Sn materials could also lead to higher temperature superconductors, further reducing the cost of cryogenics. Another approach to achieving higher performance SRF cavities has been the fabrication of Nb3Sn SRF cavities. State-of the-Art Nb3Sn SRF cavity fabrication involves Sn diffusion into a bulk Nb cavity. While encouraging results for Eacc and Q0 have been obtained for this approach, fundamental limitations in performance may still exist in trying to utilize older/pre-existing Nb cavity scaffolds/substrates that were previously fabricated with inferior bulk Nb material. More importantly, costs for new cavity construction still remain high due to the underlying scaffold material consisting of expensive bulk Nb. A new approach to Nb3Sn SRF cavity fabrication that offers both superior RF performance while replacing the expensive bulk Nb scaffold with a lower cost alternative that possess the necessary mechanical and thermal performance would be highly desirous and provides the motivation for the proposed effort. Energy-to-Power Solutions (e2P) of Tallahassee, FL in collaboration with the Thomas Jefferson National Accelerator Facility (TJNAF), ExOne Corporation, and the Hackett-Brass Foundry, proposes a revolutionary approach to Nb3Sn SRF cavity fabrication using a synergistic technologies consisting of high quality Nb thin films deposited on low cost bulk “casted” bronze (Cu-Sn) substrates. e2P’s proposed Nb3Sn SRF cavity fabrication process has its historical roots in the so-called “Bronze Route” (BR) wire/tape process that was thoroughly researched and developed decades previously and is still used today in the large scale CS and TF magnets being developed for ITER. In addition to further reduce fabrication costs and development times; the proposed bronze “casted molds” will be manufactured using an extremely low cost, rapid, and proven process. This process could lead to the revolutionary breakthrough needed for next generation Nb3Sn SRF cavity development.