Development of a 3 T Conduction-Cooled Animal MRI Superconducting Magnet With a 300 mm Warm Bore

A 3 T conduction-cooled animal MRI superconducting magnet was designed, fabricated, and tested. The MRI magnet has a large clear warm bore of Ø300 mm and a center magnetic field strength of 3 T with the measured peak-to-peak homogeneity of 217 ppm in a 180 mm diameter sphere. The magnet consists of 8 coaxial coils placed symmetrically along the axial direction. All coils made with NbTi/Cu superconducting wires were connected in series and were operated with a current of 110 A with a stored energy of about 0.62 MJ. Passive protection based on a subdivided scheme and heater network design is adopted to protect the magnet from damage caused by a quench. A two-stage GM cryocooler with a second-stage cooling power of 1.8 W is used to cool the 3 T animal MRI magnet from room temperature to 4.2 K. In this paper, magnetic design, quench protection, fabrication, and test are presented.