Development of an 11 T BSCCO Insert Coil for a 25 T Cryogen-free Superconducting Magnet

We have developed and installed an 11 T Bi
₂
Sr
₂
Ca
₂
Cu
₃
O
_y
(BSCCO) insert coil for a 25 T cryogen-free superconducting magnet (25 T-CSM). The insert coil composed of a stack of 38 double pancakes was wound with DI-BSCCO
^™
Type HT-NX conductors which had high critical tensile strength of 400 MPa at 77 K. The insert coil is cooled by two two-stage Gifford-McMahon cryocoolers and the operation temperature of the insert coil is designed to be below 10 K. The insert coil has successfully generated 11.48 T without a background field and 24.57 T with a 14.0 T background field produced by outer low temperature superconducting coils in a 52 mm room temperature bore. Before the performance test, we fabricated and tested an R&D insert coil consisting of two double pancakes, which had the same configuration as the actual insert coil pancakes do, to confirm mechanical strength of the conductors.