Nb3Sn superconducting radiofrequency cavities: development and applications

Nb3Sn superconducting radiofrequency (SRF) cavities are a promising new technology for particle accelerators. Nb3Sn's critical temperature ~18 K is approximately twice as high as the standard SRF material niobium ~9 K, allowing Nb3Sn cavities to have high Q ~10^10 even at 4 K for frequencies ~1 GHz. This could allow for significantly improved efficiency for large accelerators and could enable new applications for small industrial accelerators using small cryocoolers and conduction cooling instead of large liquid helium refrigerators. Fermilab's Nb3Sn SRF program involves material development including studies of growth, post-treatment, and microstructure, as well as prototyping for applications. Recently, Fermilab's Nb3Sn cavities have started development also towards quantum sensing for dark matter searches. In this contribution, we overview the program and recent results.