Chinese Journal of Magnetic Resonance >

2026 , Vol. 43 >Issue 3: 253 - 267

DOI: https://doi.org/10.11938/cjmr20263205

Articles

Research on Large-bore and High Homogeneity Halbach Magnet for Nuclear Magnetic Resonance

  • LIU Wanzhen ,
  • CHEN Fang ,
  • CHEN Li ,
  • WANG Jiaxin ,
  • CHENG Xin ,
  • YI Peng ,
  • ZHANG Zhi ,
  • LIU Chaoyang
Expand
  • 1 State Key Laboratory of Magnetic Resonance Spectroscopy and Imaging, National Center for Magnetic Resonance in Wuhan, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
    2 University of Chinese Academy of Sciences, Beijing 100049, China

Received date: 2026-02-05

  Online published: 2026-08-11

Fold

Abstract

Halbach permanent magnets hold significant promise for low-field nuclear magnetic resonance (LF-NMR) applications, such as rock core analysis, owing to their yoke-free design and low external stray fields. Compared with small rock cores, large rock cores better preserve the original internal structure and fluid distribution, yet they demand a larger homogeneous region. However, the complex structure of Halbach magnets inherently yields inadequate initial homogeneity, making it difficult to directly obtain a sufficiently large homogeneous region. In this study, we defined a 100-mm-diameter spherical region of interest (ROI) and optimized the magnet structure using Halbach magnet theory and finite-element simulations. The final designed magnet provides a field strength of 158.4 mT and an initial homogeneity of 22 502 ppm (1 ppm=10-6). We applied an improved harmonic-based passive shimming method and enhanced the field homogeneity to 1 496 ppm. After passive shimming, we acquired 1H free induction decay (FID) signals from an aqueous CuSO4 sample (Φ 100 mm × H 100 mm), and Carr-Purcell-Meiboom-Gill (CPMG) signals from a two-component CuSO4 aqueous solution, and distinguished different samples based on their T2. These results demonstrate that the proposed magnet design and passive shimming method are effective for constructing large-bore, high homogeneity Halbach magnets.

Key words： NMR; Halbach magnet; magnet design; passive shimming; magnetic field homogeneity

Cite this article

LIU Wanzhen , CHEN Fang , CHEN Li , WANG Jiaxin , CHENG Xin , YI Peng , ZHANG Zhi , LIU Chaoyang . Research on Large-bore and High Homogeneity Halbach Magnet for Nuclear Magnetic Resonance[J]. Chinese Journal of Magnetic Resonance, 2026 , 43(3) : 253 -267 . DOI: 10.11938/cjmr20263205

References

[1] BLüMICH B, CASANOVA F, APPELT S. NMR at low magnetic fields[J]. Chem Phys Lett, 2009, 477(4-6): 231-240.
[2] LUO G, XIAO L, LUO S, et al. A study on multi-exponential inversion of nuclear magnetic resonance relaxation data using deep learning[J]. J Magn Reson, 2023, 346: 107358.
[3] CHEN Y A, MATHUR S, LIN A, et al. Tips and challenges for clinical use and interpretation of low field portable MRI in neuroimaging[J]. Emerg Radiol, 2025, 32(2): 279-289.
[4] MITCHELL J, FORDHAM E J. Contributed review: nuclear magnetic resonance core analysis at 0.3 T[J]. Rev Sci Instrum, 2014, 85(11): 111502.
[5] DERNAIKA M, SERAG S, KALAM M Z. The impact of heterogeneity and multi-scale measurements on reservoir characterization and STOOIP estimations[C]// International Symposium of the Society of Core Analysts. Austin: SCA, 2011: 1-6.
[6] JONES M, APTAKER P S, COX J, et al. A transportable magnetic resonance imaging system for in situ measurements of living trees: the Tree Hugger[J]. J Magn Reson, 2012, 218: 133-140.
[7] SUN Z, XIAO L Z, LIAO G Z, et al. Design of magnets for in situ NMR detection devices intended for preservation of ancient architectures[J]. Chinese J Magn Reson, 2017, 34(3): 372-382.
  孙哲, 肖立志, 廖广志, 等. 用于长城等古建筑探测的NMR探测器的磁体设计[J]. 波谱学杂志, 2017, 34(3): 372-382.
[8] YU D J, GUO P, WU J M, et al. A unilateral nuclear magnetic resonance sensor for nondestructive wood moisture measurements[J]. Chinese J Magn Reson, 2017, 34(4): 508-518.
  余登洁, 郭盼, 吴嘉敏, 等. 用于木材水分检测的单边核磁共振传感器设计[J]. 波谱学杂志, 2017, 34(4): 508-518.
[9] VAN BEEK T A. Low-field benchtop NMR spectroscopy: status and prospects in natural product analysis (dagger)[J]. Phytochem Anal, 2021, 32(1): 24-37.
[10] LIU M, QIU W Q, SUN H J, et al. Research progress of portable NMR spectrometers[J]. Chinese J Magn Reson, 2014, 31(4): 504-514.
  刘敏, 邱雯绮, 孙惠军, 等. 便携式核磁共振谱仪的研究进展[J]. 波谱学杂志, 2014, 31(4): 504-514.
[11] YU P, XU Y, WU Z, et al. A low-cost home-built NMR using Halbach magnet[J]. J Magn Reson, 2018, 294: 162-168.
[12] ASTAING-CORDIER T, BOUILLAUD D, FARJON J, et al. Recent advances in benchtop NMR spectroscopy and its applications[M]//WEBB G A.Annual Reports on NMR Spectroscopy. London: Academic Press, 2021, 103: 191-258.
[13] YE Y, SHEN S, GUO P, et al. A portable Halbach NMR sensor for detecting the moisture content of soybeans[J]. IEEE Trans Instrum Meas, 2022, 71: 1-11.
[14] PURCHASE A R, VIDARSSON L, WACHOWICZ K, et al. A short and light, sparse dipolar Halbach magnet for MRI[J]. IEEE Access, 2021, 9: 95294-95303.
[15] GAO M, LUO S, ZHU L, et al. Easy-to-implement passive shimming approach of Halbach magnet for low-field NMR measurement[J]. J Magn Reson, 2025, 376: 107887.
[16] YANG L, CHEN F, CHEN L, et al. An easy-built Halbach magnet for LF-NMR with high homogeneity using optimized target-field passive shimming method[J]. J Magn Reson, 2023, 357: 107582.
[17] O'REILLY T, TEEUWISSE W M, WEBB A G. Three-dimensional MRI in a homogenous 27?cm diameter bore Halbach array magnet[J]. J Magn Reson, 2019, 307: 106578.
[18] HALBACH K. Perturbation effects in segmented rare earth cobalt multipole magnets[J]. Nucl Instrum Methods Phys Res, 1982, 198(2): 213-215.
[19] HALBACH K. Design of permanent multipole magnets with oriented rare earth cobalt material[J]. Nucl Instrum Methods Phys Res, 1980, 169(1): 1-10.
[20] TUREK K, LISZKOWSKI P. Magnetic field homogeneity perturbations in finite Halbach dipole magnets[J]. J Magn Reson, 2014, 238: 52-62.
[21] WANG J, JIANG X, HU Z, et al. Design and shimming method of low length-to-interdiameter ratio Halbach magnet[J]. IEEE Trans Instrum Meas, 2022, 71: 1-10.
[22] WINDT C W, SOLTNER H, VAN DUSSCHOTEN D, et al. A portable Halbach magnet that can be opened and closed without force: the NMR-CUFF[J]. J Magn Reson, 2011, 208(1): 27-33.
[23] ANFEROVA S, ANFEROV V, ARNOLD J, et al. Improved Halbach sensor for NMR scanning of drill cores[J]. Magn Reson Imaging, 2007, 25(4): 474-480.
[24] YU P, WANG Y, XU Y, et al. Theoretical foundation for designing multilayer Halbach array magnets for benchtop NMR and MRI[J]. J Magn Reson, 2022, 344: 107322.
[25] WANG Y, XU Y, WANG F, et al. A passive shimming method for Halbach magnet based on magnetic sheet arrays[J]. J Magn Reson, 2022, 339: 107210.
[26] JACHMANN R C, TREASE D R, BOUCHARD L S, et al. Multipole shimming of permanent magnets using harmonic corrector rings[J]. Rev Sci Instrum, 2007, 78(3): 035115.
Options
Outlines

/

〈 〉

Copyright © 2017 Editorial Board of Chinese Journal of Magnetic Resonance
Powered by Beijing Magtech Co. Ltd