Superconducting Materials in High Magnetic Fields for High Energy Physics Quantum Sensing Applications*

For quantum sensing applications in high energy physics, such as searching for dark matter axion particles, there is a need for resonators that maintain a high quality factor (Q0) in multi-tesla magnetic fields. Superconducting radiofrequency (SRF) cavities are promising candidates, but their potential for high Q0 in large magnetic fields is not well explored yet. In this contribution, we describe efforts from the SQMS Center at Fermilab to explore the potential of Nb3Sn SRF cavities in this regime. These efforts leverage previous investments in Nb3Sn cavities for particle acceleration applications. Results from measurements of Nb3Sn cavities in 6 T magnetic fields at liquid helium temperatures are presented. The outlook for future experiments in the mK regime is also discussed.