Development of Superconducting Split Magnets for NMR Spectrometer

We have developed a high-resolution NMR spectrometer with a superconducting split magnet and a cross-shaped bore. Because of the spatial limitations of the magnet´s structural design, the split magnet requires many pairs of coils to generate a high magnetic field. For this reason, it is difficult to compare the high stability and homogeneity of its magnetic field to conventional NMR magnets. Therefore, we have developed advanced superconducting magnet technologies and successfully fabricated two types of self-shielded superconducting split-magnet systems: a 7 T (300 MHz) and a 14 T (600 MHz) magnet system. The 300 MHz system consists of 12 NbTi coils with 15 joints and a stored energy of 0.7 MJ; it achieved a field drift of about 0.1 Hz/h in persistent current mode operation. The 600 MHz magnet system consists of 12 Nb₃Sn coils and 8 NbTi coils with 53 joints and a stored energy of 10 MJ. Its field drift was less than 1 Hz/h.