中国物理B ›› 2018, Vol. 27 ›› Issue (10): 104101-104101.doi: 10.1088/1674-1056/27/10/104101

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Shim coil design for Halbach magnet by equivalent magnetic dipole method

Jia-Min Wu(吴嘉敏), Zheng Xu(徐征), Pan Guo(郭盼), Jin-Feng Qi(戚金凤), Yu-Cheng He(贺玉成)   

  1. 1 State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China;
    2 School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China
  • 收稿日期:2018-05-18 修回日期:2018-06-12 出版日期:2018-10-05 发布日期:2018-10-05
  • 通讯作者: Zheng Xu, Pan Guo E-mail:xuzheng@cqu.edu.cn;guopan@cqnu.edu.cn
  • 基金资助:

    Project supported by the State Key Development Program for Basic Research of China (Grant No. 2014CB541602), the National Natural Science Foundation of China (Grant Nos. 51677008 and 51707028), and the Fundamental Research Funds of Central Universities, China (Grant No. 106112015CDJXY150003).

Shim coil design for Halbach magnet by equivalent magnetic dipole method

Jia-Min Wu(吴嘉敏)1, Zheng Xu(徐征)1, Pan Guo(郭盼)2, Jin-Feng Qi(戚金凤)1, Yu-Cheng He(贺玉成)1   

  1. 1 State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China;
    2 School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China
  • Received:2018-05-18 Revised:2018-06-12 Online:2018-10-05 Published:2018-10-05
  • Contact: Zheng Xu, Pan Guo E-mail:xuzheng@cqu.edu.cn;guopan@cqnu.edu.cn
  • Supported by:

    Project supported by the State Key Development Program for Basic Research of China (Grant No. 2014CB541602), the National Natural Science Foundation of China (Grant Nos. 51677008 and 51707028), and the Fundamental Research Funds of Central Universities, China (Grant No. 106112015CDJXY150003).

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摘要：

Low-field nuclear magnetic resonance magnet (2 MHz) is required for rock core analysis. However, due to its low field strength, it is hard to achieve a high uniform B0 field only by using the passive shimming. Therefore, active shimming is necessarily used to further improve uniformity for Halbach magnet. In this work, an equivalent magnetic dipole method is presented for designing shim coils. The minimization of the coil power dissipation is considered as an optimal object to minimize coil heating effect, and the deviation from the target field is selected as a penalty function term. The lsqnonlin optimization toolbox of MATLAB is used to solve the optimization problem. Eight shim coils are obtained in accordance with the contour of the stream function. We simulate each shim coil by ANSYS Maxwell software to verify the validity of the designed coils. Measurement results of the field distribution of these coils are consistent with those of the target fields. The uniformity of the B0 field is improved from 114.2 ppm to 26.9 ppm after using these shim coils.

关键词: equivalent magnetic dipole method, shim coils, magnetic resonance, Halbach magnet

Abstract:

Low-field nuclear magnetic resonance magnet (2 MHz) is required for rock core analysis. However, due to its low field strength, it is hard to achieve a high uniform B0 field only by using the passive shimming. Therefore, active shimming is necessarily used to further improve uniformity for Halbach magnet. In this work, an equivalent magnetic dipole method is presented for designing shim coils. The minimization of the coil power dissipation is considered as an optimal object to minimize coil heating effect, and the deviation from the target field is selected as a penalty function term. The lsqnonlin optimization toolbox of MATLAB is used to solve the optimization problem. Eight shim coils are obtained in accordance with the contour of the stream function. We simulate each shim coil by ANSYS Maxwell software to verify the validity of the designed coils. Measurement results of the field distribution of these coils are consistent with those of the target fields. The uniformity of the B0 field is improved from 114.2 ppm to 26.9 ppm after using these shim coils.

Key words: equivalent magnetic dipole method, shim coils, magnetic resonance, Halbach magnet

中图分类号:  (Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems)

  • 41.20.Gz
02.60.Pn (Numerical optimization)