Surface Impedance Measurements on Nb3Sn in High Magnetic Fields

Nb3Sn is a superconductor of great relevance for perspective radiofrequency (RF) applications. We present for the first time surface impedance (Zs ) measurements at 15 GHz and low-RF field amplitude on Nb3Sn in high magnetic fields up to 12 T, with the aim of increasing the knowledge of Nb3Sn behavior in such conditions. Zs is a fundamental material parameter that directly gives useful information about the dissipative and reactive phenomena when the superconductor is subjected to high-frequency excitations. Therefore, we present an analysis of the measured Zs with the aim of extracting interesting data about pinning in Nb3Sn at high frequencies. From Zs, we extract the vortex motion complex resistivity to obtain the r-parameter and the depinning frequency nup in high magnetic fields. The comparison of the results with the literature shows that the measured nup on bulk Nb3Sn is several times greater than that of pure Nb. This demonstrates how Nb3Sn can be a good candidate for RF technological applications, also in high magnetic fields.