Development of $\hbox {Nb}_{3}\hbox {Sn}$ Superconducting Coil Manufacture Technology

The nuclear magnetic resonance superconducting magnet technology is being developed in our laboratory. Because the upper critical magnetic field of NbTi alloy is not high enough, an Nb₃Sn superconductor has to be used in the manufacture of magnets for 500 MHz and above. In this paper, an experimental Nb₃Sn superconducting coil was manufactured to study the fabrication technology. The bobbin with Al₂O₃ ceramic coating is made of stainless steel. A vertical tube type vacuum heat treatment furnace was established for Nb₃Sn formation. Heat treatment parameters for the Nb₃Sn coil were done at 670^°C in vacuum. Vacuum pressure impregnation was done to strengthen the assembly. The Nb₃Sn coil, the switch, and the current leads were joined together using superconducting solder matrix replacement method. In the test the maximum current of the Nb₃Sn coil was 263 A, corresponding to a central magnetic field of 3.47 T. Persistent current mode operation was also successfully performed.