Achievement of 1020 MHz NMR

Abstract

We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially ±0.8ppm/10h without the (2)H lock operation; it was then stabilized to be less than 1ppb/10h by using an NMR internal lock operation. The full-width at half maximum of a (1)H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7Hz (0.7ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170ppb/10h, sufficient for NMR measurements for quadrupolar nuclei such as (17)O; a (17)O NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra.

NMR spectroscopy up to 35.2 T using a series-connected hybrid magnet

“…While HTS materials were discovered more than 30 years ago, progress in using these materials at fields above 23.5 T has been slow. An NMR magnet with an HTS insert operated for a while at 1020 MHz at Riken [4] and a non-NMR magnet with an HTS insert became operational at 24.5 T in Sendai, Japan early in 2017 [22]. Consequently, a resistive/SC hybrid was clearly the only option when this project was initiated.…”

“…Prospects for much higher magnetic fields B 0 lie primarily with high temperature superconductors (HTS) [4]. While these material developments have been making good progress over the past 30 years, the US National High Magnetic Field Laboratory (NHMFL) has designed, constructed and demonstrate here a new series-connected resistive/superconducting hybrid (SCH) magnet that operates in powered mode at fields up to 35.2 T or 1.5 GHz.…”

24 T High-Resolution and -Sensitivity Solid-State NMR Measurements of Low-Gamma Half-Integer Quadrupolar Nuclei 35Cl and 37Cl

“…The details of the LTS/HTS magnet can be found elsewhere. 18 While a double resonance HX-MAS probe with 3.2 mm stator was used at 14.1 T, a single resonance X-MAS probe with a 4.0-mm stator was used for NMR measurements at 24.0 T. The spinning frequency was actively controlled by pneumatic valves so as to achieve spinning fluctuations of less than ±10 Hz. All the experiments were performed at room temperature.…”

“…However, it has been shown recently that a highly stable hybrid magnet developed from a combination of LTS and high-temperature superconductor (HTS) is capable of breaking this barrier so as to achieve a 1 H Larmor frequency as high as 1.02 GHz. 17,18 Though, the resolution enhancement at the ultra-high magnetic field can easily be calculated from analytical equations, the sensitivity enhancement is more difficult to predict.…”

NMR of Macromolecular Assemblies and Machines at 1 GHz and Beyond: New Transformative Opportunities for Molecular Structural Biology

“…One critical achievement toward progress in the fields of structural biology, materials science, and clinical imaging (to name just a few) has been the development of higher magnetic field strengths (1–4). Higher magnetic fields yield profound improvements in both sensitivity and resolution.…”