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

• Published in: Journal of magnetic resonance (1997) Vol. 284; pp. 125 - 136
• Main Authors: Gan, Zhehong, Hung, Ivan, Wang, Xiaoling, Paulino, Joana, Wu, Gang, Litvak, Ilya M., Gor'kov, Peter L., Brey, William W., Lendi, Pietro, Schiano, Jeffrey L., Bird, Mark D., Dixon, Iain R., Toth, Jack, Boebinger, Gregory S., Cross, Timothy A.
• Format: Journal Article
• Language: English
• Published: 01.11.2017
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2017.08.007

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 7 Li lock sample doped with paramagnetic MnCl 2 . The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at 1 H 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.