Superconducting Nb3Sn cavities with high quality factors and high critical flux densities

As considerable progress is expected to result from the use of high-Tc superconductors at microwave frequencies, we started a study of the microwave properties of Nb3Sn. Preparation was done by exposing niobium cavities to a saturated tin atmosphere. Microwave measurements of the unloaded quality factor Q0 and the critical flux density Bacc were performed in the TE011 mode at 9.5 GHz. At 1.5 K low-field values of Q0 up to 6×109 and Bacc values up to 100 mT with a Q0 of 2.3×109 were obtained. At 4.2 K and at low magnetic flux densities a Q0 of 2.7×109 was reached.