A cryocooler-cooled 10 T superconducting magnet with 100 mm room temperature bore

A NbTi/Nb₃Sn superconducting magnet directly cooled by a 4 K cryocooler has been fabricated. It successfully attained a 10 T field at the center of a 100 mm room temperature bore. A 4 K Gifford-McMahon (GM) cryocooler, using Er₃Ni regenerator, cools the magnet without the use of liquid helium. Bi₂Sr₂CaCu₂O_y superconducting power leads were adopted to reduce heat input to the 4 K stage. The coil heat is removed through heat conducting copper cylinders. The coil winding is epoxy-impregnated without a bore tube to stabilize the magnet against quenching. Two diode shunt circuits are placed in the cryostat to protect the coils. A fast ramp of 10 T/20 min, was attained by reducing Nb₃Sn conductor hysteresis loss and by decreasing the contact resistance between the coil and the conduction cylinder