The discovery of high Tc superconductors has led to the development of novel applications of bulk materials for practical industries, as well to the application of the wiring for metallic low-temperature superconductors. Uniform REBCO bulk materials have been successfully manufactured with the size reaching more than 60 mm in diameter, and these cylindrical superconducting bulk magnets have created applications for compact cryogen-free NMR magnets. In the latest research, a newly designed magnet composed of eight-stacked bulk magnets has been developed. Furthermore, a GdBCO tape was wound around the copper pipe, and this was inserted into the bore of the magnet. The NMR spectrum resolution of 1 Hz at the full width at half maximum was observed on this magnet. This proved that the magnetic field homogeneity required for the high-resolution NMR has been accomplished using a cylindrical superconducting bulk magnet. In the near future, the mechanical strength of the bulk superconductor itself will be improved, leading to the common use of 400 MHz (9.4 T) NMR magnets.
Compact NMR magnets comprised of stacked HTS bulk annuli trapped using a field cooling (FC) method and cooled by liquid nitrogen have been developed. The strength and homogeneity of the magnetic field required for the NMR relaxometry device are 1.5 T and 150 ppm/cm3, respectively, and these