Development of 14 T superconducting magnet with active shield

We have designed and manufactured the superconducting magnet to generate 14 T at the center of the magnet. The diameter of the magnet bore is 64 mm. The homogeneity of magnetic field at the magnet center is estimated to be 10-5 inside the spherical volume with 5 mm diameter. The magnet is composed of three kinds of conductors and consists of four coil assemblies. Two inner coils were wound with multifilamentary (NbTi)3Sn and Nb3Sn superconductor. These coils were fabricated by Wind and React Method under certain conditions determined by preliminary experiments. After heat treatment, both coils were impregnated with epoxy resin simultaneously in order to fix the conductor around each bobbin. Two outer coils, so-called backup and active shield coil, were wound with multifilamentary NbTi superconductor. The NbTi coil assemblies were constructed with Formvar insulated wire wound tightly around the bobbins without impregnation. In order to decrease the leakage flux from the magnet and to lighten the magnet weight, we have adopted the active shield method instead of the iron shield method, therefore the magnetic shield weight has been reduced to 18% as compared with the iron shield weight. This paper describes the design and also manufacturing of the magnet. (author)