Application of a compact cryogen-free superconducting bulk magnet to NMR. Evaluation of a superconducting bulk magnet using NMR signal

A compact cryogen-free NMR magnet was developed using annular bulk superconductors. The superconducting bulk magnet is energized using a field-cooling (FC) method operated at 4.7 T. Two magnets with different configurations are proposed and investigated. One magnet consists of three GdBaCuO and two SmBaCuO bulks with outer diameters (OD) of 60 mm, inner diameters (ID) of 16 mm and a total height of 60 mm. The GdBaCuO bulks that have higher relative magnetic permeability (1.01) are sandwiched between the SmBaCuO bulks that have lower permeability (1.0003). The other magnet consists of four EuBaCuO bulks with a permeability of 1.001, OD of 60 mm, ID of 16 mm and height of 70 mm. Using these magnets, we observed a chemical shift of toluene 1H NMR spectra and confirmed that the bulk magnets generated a magnetic field with homogeneity less than 0.5 ppm from the full width at half the maximum (FWHM) of a methyl proton signal of toluene. Magnetic field stability of less than 0.02 μT/hour was achieved in the EuBaCuO bulk magnet. (author)