Fabrication of a 10 tesla cryogen-free superconducting magnet

A superconducting magnet with the center magnetic field of 10 T and warm bore size of 100 mm was designed and fabricated. The magnet coils were fabricated with NbTi and Nb₃Sn superconducting wires. The NbTi and Nb₃Sn coils were manufactured with inter-winding support structure. A cryostat was designed and fabricated to accommodate the magnet with an outer diameter of 740 mm and height of 560 mm. The magnet system was cooled by a GM cryocooler with cooling capacities of 35 W at the first stage and 1.5 W at the second stage cold head. A pair of Bi2223 bulk high temperature current leads were employed to reduce heat leakage to the magnet. Total weight of the magnet system is about 230 kg. The superconducting magnet can be cooled down to 4.1 K in 90 hours with the cryocooler. The magnet was tested and reached the maximum operating current of 119.4 A, corresponding to a center magnetic field of 10.25 T in the warm bore. No quench was observed during the test process. It shows that the magnet stability is improved with the inter-winding support structure in magnet coil fabrication. The superconducting magnet system has been operating stably for several months. Extensive experiments on magnetic separation have been done on the magnet setup. In this paper, the detailed information of magnet design, fabrication and test are presented.