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

Abstract

The National High Magnetic Field Laboratory has brought to field a Series-Connected Hybrid magnet for NMR spectroscopy. As a DC powered magnet it can be operated at fields up to 36.1 T. The series connection between a superconducting outsert and a resistive insert dramatically minimizes the high frequency fluctuations of the magnetic field typically observed in purely resistive magnets. Current-density-grading among various resistive coils was used for improved field homogeneity. The 48 mm magnet bore and 42 mm outer diameter of the probes leaves limited space for conventional shims and consequently a combination of resistive and ferromagnetic shims are used. Field maps corrected for field instabilities were obtained and shimming achieved better than 1 ppm homogeneity over a cylindrical volume of 1 cm diameter and height. The magnetic field is regulated within 0.2 ppm using an external 7Li lock sample doped with paramagnetic MnCl2. The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at 1H frequencies of 1.0, 1.2 and 1.5 GHz. NMR at 1.5 GHz reflects a 50% increase in field strength above the highest superconducting magnets available presently. Three NMR probes have been constructed each equipped with an external lock rf coil for field regulation. Initial NMR results obtained from the SCH magnet using these probes illustrate the very exciting potential of ultra-high magnetic fields.

Probing Interactions of γ‐Alumina with Water via Multinuclear Solid‐State NMR Spectroscopy

“…In order to increase the spectral resolution and distinguish the Al ions with different coordination numbers, 27 Al MAS NMR spectra of both dehydrated and hydrated alumina were collected at an ultrahigh field of 35.2 T using the Series-Connected-Hybrid magnet at the National High Magnetic Field Laboratory of the U. S. [19] With the reduction of quadrupole broadening, three peaks at approx. 71, 34 and 12 ppm can be observed for both samples, which can be readily assigned to 4-, 5-and 6-coordinated Al ions, respectively ( Figure 1 and Figure S5).…”

High magnetic fields for fundamental physics

“…Connecting the superconducting outsert and the resistive insert in series has the benefit of significantly reducing, due to the large inductance of the superconducting magnet, the high-frequency magnetic field fluctuations that are otherwise typically present in purely resistive Bitter-type magnets. The result is an extremely "quiet" magnetic field that is well suited to precision measurements requiring high stability (e.g., spin resonance [152]). A 36 T series-connected hybrid magnet with a 40 mm warm bore and ≈ 1 ppm uniformity over 1 cm 3 was recently developed and tested at the NHMFL in Tallahassee [153,154].…”

A Quadrupole‐Central‐Transition 59Co NMR Study of Cobalamins in Solution

“…15000 ppm. Furthermore, if the 59 Co QCT NMR can be performed at 35.2 T, the minimum line width would be reduced to as small as 15 ppm for CNCbl. It is also important to note that the minimum line width is generally observed when ω 0 τ C ≈20–100.…”

“…While the QCT NMR methodology has been known for a long time, its applications are scare in the literature. In recent years, there has been renewed interest in QCT NMR applications, largely because the availability of very high magnetic fields as well as the demonstration of QCT NMR studies of biologically important quadrupolar nuclei such as 17 O ( I =5/2) . In this work, we set out to explore whether 59 Co QCT signals can be detected in Cbl molecules and to investigate the best conditions of detecting 59 Co QCT NMR signals in general.…”