Performances of a 400kJ-Class Pulsed Superconducting Magnet and its Considerations

A pulsed magnet with stored energy of 363kJ has been developed. The central field is 3T at 2100A. The conductor is a braid which is composed of 120 strands with a mixed matrix (Cu and CuNi) and is not solder-filled and thus not mechanically rigid. The magnet consists of 25 double pancake coils and the size is 40cm, 50cm and 59.2cm in i.d., o.d. and axial length, respectively. Turn to turn insulation is provided by a 0.5mm thick and 6mm wide semi-cured epoxy glass-cloth tape, which is wound about the braid, for the 13 double pancake coils, and by a cured epoxy glass-cloth tape for the other coils. The semi-cured tape is heat treated after winding. The magnet was charged at a sweep rate of about 0.05T/sec up to 2250A without quenching where the stored energy was about 418kJ. In pulse operations, it was charged to 3T in about 5 seconds and discharged to zero in about 1.65 seconds without quenching. At a faster charging rate, however, it was quenched. During the charge, major conductor motion was observed in parts of the double pancake coils wound with the braid wrapped with the cured tape, and hence the quenching will be attributed to the conductor motion. We are now rewinding those double pancake coils by using the braid wrapped with semi-cured epoxy glass-cloth tape.