A low-cost, miniature Halbach magnet designed for portable time domain NMR

Article type: Research Article

Authors: Yang, Qing^{a; b} | Wang, Junnan^{a; b} | Hu, Zhu^{a; b} | Ni, Zhonghua^{a; b} | Lu, Rongsheng^{a; b;} | Yi, Hong^{a; b;}

Affiliations: [a] School of Mechanical Engineering, Southeast University, Nanjing, China | [b] Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Nanjing, China

Correspondence: [*] Corresponding authors: Rongsheng Lu, School of Mechanical Engineering, Southeast University, Nanjing, 210000, China. Tel.: +86 18020111699; E-mail: lurs@seu.edu.cn. Hong Yi, School of Mechanical Engineering, Southeast University, Nanjing, 210000, China. E-mail: yihong@seu.edu.cn

Abstract: In this paper, a new portable, low-cost magnet with a good homogeneity is presented. The single-layer central magnet structure based on Halbach-type array has been designed, simulated which can generate a magnetic field of 1 T under the weight of 2 kg. Magnetic strips placed at the ends of the central magnet are presented to improve the central homogeneity. In order to counteract the inhomogeneity resulting from manufacturing tolerances, a new compact shimming structure designed for miniature Halbach magnet is applied. With this structure a reduction of the full width at half maximum (FWHM) from 21 kHz to less than only 0.7 kHz, which is adequate for achieving a good NMR relaxation signal. This novel miniature magnet structure has achieved an excellent balance between cost and homogeneity for portable time domain NMR.

Keywords: Halbach magnet, passive shimming, linear programming, portable NMR, FEM simulations

DOI: 10.3233/JAE-200001

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 65, no. 1, pp. 59-73, 2021