Nb₃Sn Coating of Complex Accelerator Cavity Structures

In the accelerator science field, most of the superconducting accelerator cavities are currently made out of niobium. Cavities coated with superconducting thin films with the potential to reduce the cost and improve the cavity performance are essential to the modern Superconducting Radio Frequency (SRF) accelerator research. Within the potential superconducting thin film materials, Nb₃Sn with its higher critical temperature and superheating field (both twice that of Nb) promises superior performance, notable cost reduction, and higher operating temperatures than Nb. The Sn vapor diffusion method is the most successful technique so far to coat niobium cavities with Nb₃Sn. Although there are several basic cavity models coated with Nb3Sn and tested at their specific frequencies, there is limited coating experience with complex cavity geometries to investigate Nb₃Sn potential for accelerator applications. This paper discusses recent progress made on the Nb₃Sn coating of the twin axis cavity at Jefferson Lab. This cavity with relatively complex geometry is proposed for energy recovery linac applications and will be helpful with measuring the superconducting properties of the Nb₃Sn.