Achievement of 1020 MHz NMR

We have successfully developed a 1020 MHz (24.0 T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-T-c superconductors NbTi and Nb3Sn) outer coils and an HTS (high-T-c superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8 K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially +/- 0.8 ppm/10 h without the H-2 lock operation; it was then stabilized to be less than 1 ppb/10 h by using an NMR internal lock operation. The full-width at half maximum of a H-1 spectrum taken for 1% CHCl3 in acetone-d(6) was as low as 0.7 Hz (0.7 ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170 ppb/10 h, sufficient for NMR measurements for quadrupolar nuclei such as O-17; a O-17 NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra. (C) 2015 Elsevier Inc. All rights reserved.