Development of a superconducting joint for high field NMR

The innermost coil of a new high-field NMR magnet such as a 1-GHz NMR magnet is designed by using a new superconductor. It is therefore important that a superconducting joint between the new superconductor and the NbTi conductor was developed. We have developed a new superconducting joint method for the Nb3Al conductor, which is expected to be used for the innermost coil of the 1-GHz NMR magnet. This joint method uses the Nb3Sn layer that is formed on the Nb matrix surface of the Nb3Al conductor. This Nb3Sn layer enables the soldering of the Nb3Al conductor; thus, it is possible to solder the Nb3Al conductor and NbTi conductor. The superconducting property of the Nb3Al-NbTi joint that is joined by the superconducting solder (for example, SnBiPb solder) showed good performance under a magnetic field of 0.1 T.