Production of Seamless Superconducting Radio Frequency Cavities from Ultra-Fine-Grained Niobium

75616-Superconducting radio frequency cavities, used in high energy accelerators, are produced by the sheet metal forming of multiple sections, which are then joined by high-vacuum, electron-beam welding. The welding procedures are very expensive and produce flaws and contamination that limit cavity performance. Simpler approaches, based on the shaping of seamless tubes, have been hindered by limited formability and performance-limiting surface roughness. This project will develop a process for forming niobium-superconducting, radio frequency cavities from seamless tubes of ultra-fine grained niobium. Phase I will develop a method for processing bulk niobium to a highly formable, fine-grained condition and determine the suitability of this metal for low-cost forming methods. A novel metal working technique, equal channel angular extrusion, will be used to produce ultra fine grain microstructures. Mechanical testing will then be used to determine forming parameters. Commercial Applications and Other Benefits as described by the awardee: Ultra-fine grain niobium, and the shaping processes it will allow, should lower cost, reduce assembly time, and improve the performance of superconducting radio frequency accelerators.¿ Such devices are used in high-energy physics research and in Free Electron Lasers, which have potential applications in industrial processing, medical research, and weapons systems.