2026-10-13T01:51:41Z https://www.scidb.cn/oai

10.57760/sciencedb.43942 2026-08-31T10:55:14Z

2026-08-31 Research on Large-bore and High Homogeneity Halbach Magnet for Nuclear Magnetic Resonance doi:10.57760/sciencedb.43942 en 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 ma NMR; Halbach magnet; magnet design; passive shimming; magnetic field homogeneity Liu Wanzhen Chen Fang Chen Li Wang Jiaxin Yi Peng Zhang Zhi Liu Chaoyang RESTRICTED dataset Science Data Bank