Development of a miniature permanent magnetic circuit for nuclear magnetic resonance chip
Development of a miniature permanent magnetic circuit for nuclear magnetic resonance chip
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DOI：
10.3901/cjme.2013.04.689
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发表时间：
2013-08
影响因子：
4.2
通讯作者：
Rongsheng Lu;Hong Yi;Wei-Ping Wu;Z. Ni
中科院分区：
文献类型：
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作者：
Rongsheng Lu;Hong Yi;Wei-Ping Wu;Z. Ni
现有的微型磁路研究主要集中在单边永磁路和Halbach永磁路。在单面永磁路中，工作区域的磁通密度往往很低。在Halbach永磁电路中，制造和组装工艺总是有很大的困难。在信噪比(SNR)计算模型的基础上，分析了核磁共振芯片所需的静态磁通密度，并根据所需的磁通密度设计了微型C型永磁路。根据基尔霍夫定律和磁通折射原理，提出了单垫圈的概念，以提高所设计磁路的性能。采用有限元方法进行了对比计算。计算结果表明，单垫片改进后的磁路比不加垫片和双垫片的磁路具有更高的磁通密度和更好的磁场均匀度。制作了磁路，搭建了磁路实验测试平台。在工作区测得的磁通密度为0.7T，与理论设计吻合较好。磁场的空间变化在仪器误差范围内。最后，通过理论分析和实验研究，研究了该磁路产生的磁通密度与温度的关系，得到了一个线性函数模型。本文的研究对于解决核磁共振芯片在不同环境温度下的应用问题具有重要意义。
The existing researches of miniature magnetic circuits focus on the single-sided permanent magnetic circuits and the Halbach permanent magnetic circuits. In the single-sided permanent magnetic circuits, the magnetic flux density is always very low in the work region. In the Halbach permanent magnetic circuits, there are always great difficulties in the manufacturing and assembly process. The static magnetic flux density required for nuclear magnetic resonance(NMR) chip is analyzed based on the signal noise ratio(SNR) calculation model, and then a miniature C-shaped permanent magnetic circuit is designed as the required magnetic flux density. Based on Kirchhoff’s law and magnetic flux refraction principle, the concept of a single shimming ring is proposed to improve the performance of the designed magnetic circuit. Using the finite element method, a comparative calculation is conducted. The calculation results demonstrate that the magnetic circuit improved with a single shimming has higher magnetic flux density and better magnetic field homogeneity than the one improved with no shimming ring or double shimming rings. The proposed magnetic circuit is manufactured and its experimental test platform is also built. The magnetic flux density measured in the work region is 0.7 T, which is well coincided with the theoretical design. The spatial variation of the magnetic field is within the range of the instrument error. At last, the temperature dependence of the magnetic flux density produced by the proposed magnetic circuit is investigated through both theoretical analysis and experimental study, and a linear functional model is obtained. The proposed research is crucial for solving the problem in the application of NMR-chip under different environmental temperatures.