Development of a 12 T Conduction-Cooled Split-Pair Magnet With Crossing Warm Bore

A 12 T conduction-cooled split-pair magnet for material processing applications, featuring a crossing warm bore with a diameter of 101 mm in the vertical direction and 51 mm in the horizontal direction, has been designed and fabricated. The split-pair magnet has two Nb₃Sn coils and three NbTi coils symmetrically on each side. It operates at 89.55 A current and generates a center magnetic field strength of 8.78 T and a maximum magnetic field strength of 12 T in the central axis of the crossing warm bore. The magnet's inductance is 505.1 H and its stored energy is 2.03 MJ. A passive protection circuit composed of coil subdivision and quench initiating heater has been selected to protect the magnet from damage caused by quenching. The magnet is integrated into a conduction-cooled cryostat and directly cooled by two Gifford W E and McMahon H O (GM) cryocoolers with a 1.8 W cooling power in the second stage. The detailed electromagnetic design, quench protection design, cryostat design, fabrication, and test of this 12 T split-pair magnet will be presented in this article.