Fabrication of Niobium Cavities Directly from Large Grain Ingot

A key impediment to the broader use and acceptance of superconducting linear accelerators has been the cost, both financial and time, of developing niobium superconducting radio frequency (SRF) structures. In the present fabrication method, the dominant costs are (1) the procurement of fine grain bulk niobium and (2) electron beam welding. This project will develop a new fabrication method for SRF cavities that greatly reduces the cost and time to deliver the cavity. The new fabrication method will use traditional metal forming techniques to shape cavity components directly from a niobium large grain ingot. This approach would eliminate the need for fine grain niobium sheet metal and would greatly reduce the number of electron beam welds necessary to fabricate SRF cavities. Phase I will develop ingot forming methods, prototype a 1.3 GHz dumbbell from a single piece of large grain ingot material, and measure the frequency to verify that dimensional tolerances are met. End cells could then be added to further check the dumbbell as a two cell cavity. Phase II would prototype the end assemblies, and build and test two 9-cell ILC cavities. Commercial Applications and other Benefits as described by the awardee: The proposed fabrication methods have the potential to cut cost and development time by half or more. The inexpensive ingot-formed cavities could be marketed to the international accelerator community.