Towards a beyond 1 GHz solid-state nuclear magnetic resonance: External lock operation in an external current mode for a 500 MHz nuclear magnetic resonance
- RIKEN Systems and Structural Biology Center, Yokohama, Kanagawa 230-0045 (Japan)
- Graduate School of Yokohama City University, Yokohama, Kanagawa 230-0045 (Japan)
- Graduate School of Chiba University, Chiba, Chiba 263-8522 (Japan)
- JEOL RESONANCE Inc., Akishima, Tokyo 196-8558 (Japan)
- Kobe Steel, Ltd., Kobe, Hyogo 651-2271 (Japan)
- Probe Laboratory Inc., Hamura, Tokyo 205-0021 (Japan)
- Superconducting Wire Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0003 (Japan)
Achieving a higher magnetic field is important for solid-state nuclear magnetic resonance (NMR). But a conventional low temperature superconducting (LTS) magnet cannot exceed 1 GHz (23.5 T) due to the critical magnetic field. Thus, we started a project to replace the Nb{sub 3}Sn innermost coil of an existing 920 MHz NMR (21.6 T) with a Bi-2223 high temperature superconducting (HTS) innermost coil. Unfortunately, the HTS magnet cannot be operated in persistent current mode; an external dc power supply is required to operate the NMR magnet, causing magnetic field fluctuations. These fluctuations can be stabilized by a field-frequency lock system based on an external NMR detection coil. We demonstrate here such a field-frequency lock system in a 500 MHz LTS NMR magnet operated in an external current mode. The system uses a {sup 7}Li sample in a microcoil as external NMR detection system. The required field compensation is calculated from the frequency of the FID as measured with a frequency counter. The system detects the FID signal, determining the FID frequency, and calculates the required compensation coil current to stabilize the sample magnetic field. The magnetic field was stabilized at 0.05 ppm/3 h for magnetic field fluctuations of around 10 ppm. This method is especially effective for a magnet with large magnetic field fluctuations. The magnetic field of the compensation coil is relatively inhomogeneous in these cases and the inhomogeneity of the compensation coil can be taken into account.
- OSTI ID:
- 22093793
- Journal Information:
- Review of Scientific Instruments, Vol. 83, Issue 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
Similar Records
On Ex Situ NMR: Developing portable low-cost and/or single sided NMR/MRI
Direct current superconducting quantum interference device spectrometer for pulsed nuclear magnetic resonance and nuclear quadrupole resonance at frequencies up to 5 MHz