A Cryocooler-Cooled 10 T Superconducting Magnet With 100 Mm Room Temperature Bore

A NbTi/Nb3Sn superconducting magnet directly cooled by a I 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. Bi2Sr2CaCu2Oy superconducting power leads were adopted to reduce heat input to the I 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.