2016 年 51 巻 7 号 p. 342-348
The world's first Nuclear Magnetic Resonance (NMR) system with an operating frequency above 1 GHz was developed and operated at the National Institute for Materials Science (NIMS) during 2014–2015. The Nb3Sn innermost coil of an existing 920 MHz (21.6 T) NMR magnet was replaced with a Bi-2223 layer-wound coil, upgrading the magnet to 1.03 GHz (24.2 T). At 1.02 GHz (24.0 T), shimming started to achieve the homogeneous magnetic field required for NMR measurements. However, large magnetic-field inhomogeneity appeared that was capable of being compensated using the superconducting (SC) and room temperature (RT) shim coils installed. We used a powerful and fast-acting shimming method that combines ferromagnetic shim, SC shim and RT shim to compensate the inhomogeneity. This achieved effective compensation of the magnetic-field inhomogeneity, subsequently leading to an excellent NMR resolution test result of 0.7 ppb (0.7 × 10-9). This NMR resolution will enable NMR measurement of a membrane protein sample.