A CRYOCOOLER COOLED 5-T SUPERCONDUCTING MAGNET WITH A HORIZONTAL AND VERTICAL ROOM-TEMPERATURE BORE

We designed and constructed a cryocooler cooled 5 T superconducting ma gnet with a horizontal room temperature bore of 50 mm and a vertical r oom temperature bore of 90 mm without liquid helium. The magnet, which is directly cooled by 4 K Gifford-McMahon cryocooler in vacuum, consi sts of NbTi coil, Bi(2223) bulk current leads and cryostat. The coil w ith an inner diameter of 130 mm, an outer diameter of 301 mm, a height of 66 mm and a gap of 80 mm is made using NbTi wires and Cu-plated SU S bobbin. Bi(2223) bulk current leads are thin-walled sintered cylindr ical tube, The outer diameter, height and weight of the magnet are 510 mm, 730 mm and 260 kg, respectively. The magnet is cooled down to 3.8 K in approximately 62 hours. A continuous operation at 5 T, which is generated by an operating current of 122 A, has been performed.