Zhehong Gan1, Ivan Hung1, Xiaoling Wang1, Joana Paulino2, Gang Wu3, Ilya M Litvak1, Peter L Gor'kov1, William W Brey1, Pietro Lendi4, Jeffrey L Schiano5, Mark D Bird1, Iain R Dixon1, Jack Toth1, Gregory S Boebinger6, Timothy A Cross7. 1. National High Magnetic Field Laboratory, Tallahassee, FL 32310, United States. 2. National High Magnetic Field Laboratory, Tallahassee, FL 32310, United States; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, United States; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, United States. 3. Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada. 4. Bruker BioSpin AG, 26, Industriestrasse Fällanden, 8117, Switzerland. 5. School of Electrical Engineering and Computer Science, Penn State University, University Park, PA 16802, United States. 6. National High Magnetic Field Laboratory, Tallahassee, FL 32310, United States; Department of Physics, Florida State University, Tallahassee, FL 32306, United States. 7. National High Magnetic Field Laboratory, Tallahassee, FL 32310, United States; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, United States; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, United States. Electronic address: cross@magnet.fsu.edu.
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 36.1T. 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 48mm magnet bore and 42mm 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 1ppm homogeneity over a cylindrical volume of 1cm diameter and height. The magnetic field is regulated within 0.2ppm 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 1.5GHz. NMR at 1.5GHz reflects a 50% increase in field strength above the highest superconducting magnets currently available. 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.
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 36.1T. 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 48mm magnet bore and 42mm 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 1ppm homogeneity over a cylindrical volume of 1cm diameter and height. The magnetic field is regulated within 0.2ppm using an external 7Li lock sample doped with paramagnetic n class="Chemical">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 1.5GHz. NMR at 1.5GHz reflects a 50% increase in field strength above the highest superconducting magnets currently available. Three NMR probes have been constructed each equipped with an external lock rfcoil for field regulation. Initial NMR results obtained from the SCH magnet using these probes illustrate the very exciting potential of ultra-high magnetic fields.
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