High Magnetic Field Superconducting Magnet With Zero Helium Boil-Off for Nuclear Magnetic Resonance Spectrometer

A superconducting magnet was designed based on the requirements of high magnetic field nuclear magnetic resonance. The superconducting coils are fabricated with the various diameters of superconducting wire to improve the performance and reduce the weight in the magnet. The superconducting magnet with the available-bore of ¿54 mm and center field of 11.75 T is cooled by the liquid helium. To reduce the liquid helium evaporation, a two-stage 4 K pulsed tube refrigerator is employed to cool the system. The actively shielded magnet has a high pure copper quench band to reduce stray field burst during a quench of the shield superconducting coil. The paper presents the electromagnetic design, and stress and protection in detail.