Fabrication and properties of QMG coil magnets

QMG is a high Jc bulk material, which consists of single crystalline 1 2 3 with finely dispersed 2 1 1. A QMG coil magnet is proposed as a high field application of oxide bulk high Tc superconductors (HTS). Since the QMG is produced in the form of a single crystal bulk, it has been considered difficult to make a coil shaped magnet by drawing it into wire and winding it into a coil like the Nb–Ti superconducting wire now commercially available. However, the latest machining techniques have made it possible to slice a QMG into a wafer whose thickness is 1 mm or less and form it into a spiral coil. We have been developing the magnets by stacking the QMG coils fabricated through such machining work and soldering them at the inner and outer ends. It can be excited by applying electric current. Presently, we have succeeded to fabricate the split-type QMG magnet that can generate a magnetic flux density of 2.3 T at 54 K. The fabrication and properties of the QMG coil magnet are reported in this paper.