Wang Ya, Liu Tingwei, Peng Bowen, Yu Peng, Yang Xiaodong, Xu Yajie
Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China.
Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China; School of Electronic and Information Engineering, Changchun University of Science and Technology, 130022 Changchun, China.
J Magn Reson. 2023 Oct;355:107559. doi: 10.1016/j.jmr.2023.107559. Epub 2023 Sep 21.
Due to production and assembly errors of magnets resulting in reduced magnetic field homogeneity, passive shimming (PS) is necessary when Halbach magnets are used in high-resolution Benchtop Nuclear Magnetic Resonance (BNMR) spectrometer. The conventional PS technique, which places independent PS devices inside the magnet aperture, is no longer applicable to small-aperture compact high-field-strength Halbach magnet studies. In this paper, based on spherical harmonic function expansion, we improve the magnetic field homogeneity by optimizing the moving step of the magnet moving arrays composed of Halbach magnets to generate the corresponding harmonic terms to compensate for the magnetic field. With this approach, the homogeneity of a 1 T Halbach magnet was improved from the original 3913 ppm to 8 ppm in a L10 mm × R2.5 mm of 0.64% copper sulfate doped water sample. This work explores the PS mechanism based on the movement of magnetic blocks, which can be applied in BNMR and other compact high-field strength high-homogeneity Halbach magnets application circumstances.
由于磁体的生产和装配误差导致磁场均匀性降低，当在高分辨率台式核磁共振（BNMR）光谱仪中使用哈尔巴赫磁体时，需要进行被动匀场（PS）。传统的PS技术是将独立的PS装置放置在磁体孔径内，该技术不再适用于小孔径紧凑型高场强哈尔巴赫磁体的研究。在本文中，基于球谐函数展开，我们通过优化由哈尔巴赫磁体组成的磁体移动阵列的移动步长来改善磁场均匀性，以产生相应的谐波项来补偿磁场。通过这种方法，在一个L10 mm×R2.5 mm的0.64%硫酸铜掺杂水样中，1 T哈尔巴赫磁体的均匀性从原来的3913 ppm提高到了8 ppm。这项工作探索了基于磁块移动的PS机制，可应用于BNMR和其他紧凑型高场强高均匀性哈尔巴赫磁体的应用场景。
