Tests on a 6 T conduction-cooled superconducting magnet

A 6 T conduction-cooled superconducting magnet was designed, fabricated and tested. The magnet is composed of two coaxial NbTi solenoid coils with identical axial length. Clear bore of the magnet is Φ 226 mm. The magnet is installed in a vacuum cryostat with a Φ 100 mm room temperature bore. The cryostat is designed in a support frame to be rotatable in a horizontal or vertical direction. A two-stage 4 K Gifford-McMahon (GM) cryocooler is used to cool down the superconducting magnet from room temperature to 4 K. The cooling power of the 4 K cold head is 1 W. A pair of Bi-2223 high temperature superconducting current leads was employed to reduce heat leakage into 4 K cold mass. Total cold mass of the superconducting magnet is about 115 kg. It takes 82 hours to cool down the magnet from 300 K to 4 K directly through the cryocooler. The superconducting magnet reached the designed central magnetic field of 6 T in the warm bore when a 115 A energizing current is applied. The superconducting magnet was stably operating more than 275 hours continuously in full field. Further, a Nb₃Sn coil insert to be installed, the magnet can provide the maximum center field of 10 T with effective warm bore of Φ 100 mm. In this paper, the detailed design, fabrication and test are presented.