Wang Ya, Xu Yajie, Wang Feng, Zhang Junhao, Peng Bowen, Yu Peng, Yu Yingcong, Yang Xiaodong
School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; 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.
J Magn Reson. 2022 Jun;339:107210. doi: 10.1016/j.jmr.2022.107210. Epub 2022 Apr 6.
Halbach magnet has great potential in nuclear magnetic resonance device, where the field homogeneity requirement puts heavy demands on high efficiencypassive shimming (PS) technique. Conventional PS involves a tedious iteration process of the magnetic block/sheet number and positions optimization. In this paper, we propose a PS method based on magnetic sheet arrays (MSAs) targeting at spherical harmonic basis up to the 3rd order including dedicated composition of Y(4Z2-X2-Y2), Z3 and X(4Z2-X2-Y2) (n = 3, m = -1,0,1) with cross terms to implement structural field compensation. With this approach, the homogeneity of a 0.5 T Halbach magnet was improved from the original 811 ppm to 4.7 ppm in a L15 mm × R2.5 mm water sample. Rough shimming in another 0.93 T Halbach magnet also improved the homogeneity from 1103 ppm to 125 ppm in R2.5 mm sphere. This work provides a flexible, convenient PS method based on MSAs for compact Halbach magnet, which can be applied in NMR spectrometers and other high homogeneity application circumstances.
哈尔巴赫磁体在核磁共振设备中具有巨大潜力，其中对磁场均匀性的要求对高效被动匀场（PS）技术提出了很高的要求。传统的被动匀场涉及磁块/磁片数量和位置优化的繁琐迭代过程。在本文中，我们提出了一种基于磁片阵列（MSA）的被动匀场方法，该方法针对高达三阶的球谐基，包括Y(4Z²-X²-Y²)、Z³和X(4Z²-X²-Y²)（n = 3，m = -1,0,1）的专用组合以及交叉项，以实现结构场补偿。通过这种方法，在一个L15 mm×R2.5 mm的水样中，0.5 T哈尔巴赫磁体的均匀性从原来的811 ppm提高到了4.7 ppm。在另一个0.93 T哈尔巴赫磁体中进行的粗调匀场也将R2.5 mm球体中的均匀性从1103 ppm提高到了125 ppm。这项工作为紧凑型哈尔巴赫磁体提供了一种基于磁片阵列的灵活、便捷的被动匀场方法，可应用于核磁共振光谱仪和其他高均匀性应用场景。
