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
National High Magnetic Field Laboratory, Tallahassee, FL 32310, United States.
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.
J Magn Reson. 2017 Nov;284:125-136. doi: 10.1016/j.jmr.2017.08.007. Epub 2017 Aug 24.
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 Li lock sample doped with paramagnetic MnCl. The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at H 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.
美国国家强磁场实验室已将一台用于核磁共振光谱的串联混合磁体投入使用。作为一台直流供电磁体，它可在高达36.1T的磁场下运行。超导外部线圈和电阻性内部线圈之间的串联连接极大地减少了在纯电阻磁体中通常观察到的磁场高频波动。通过对各种电阻性线圈进行电流密度分级来提高磁场均匀性。探头48mm的磁体孔径和42mm的外径为传统垫片留下的空间有限，因此使用了电阻性垫片和铁磁垫片的组合。获得了针对磁场不稳定性进行校正的场图，并且在直径和高度均为1cm的圆柱体积内实现了优于1ppm的均匀性匀场。使用掺杂有顺磁性MnCl的外部锂锁定样品将磁场调节在0.2ppm以内。使用改进的AVANCE NEO控制台实现的更好的磁场均匀性和磁场调节，使得能够在1.0、1.2和1.5GHz的氢频率下进行核磁共振光谱分析。1.5GHz的核磁共振反映出磁场强度比目前可用的最高超导磁体高出50%。已构建了三个核磁共振探头，每个探头都配备有用于磁场调节的外部锁定射频线圈。使用这些探头从串联混合磁体获得的初步核磁共振结果展示了超高磁场极具潜力的应用前景。
