一种用于磁共振波谱仪的主动匀场电源设计

doi:10.11938/cjmr20233066

摘要/Abstract

摘要：

高均匀度磁场是磁共振波谱仪获得高质量谱图以进行化学结构解析和动力学信息获取的重要保证，需要利用高性能匀场电源驱动匀场线圈产生补偿电磁场保证磁场均匀度．高精度、高稳定性匀场电源是提升磁共振波谱仪主动匀场性能、保持匀场效果的关键部件．本文针对磁共振波谱仪多通道主动匀场需求，开发设计了一款高精度、高稳定、多通道主动匀场电源系统．基于负反馈控制，设计带有输出状态监控的匀场电流驱动器（恒流源），搭配MCU控制平台和上位机软件完成软硬件之间控制指令和数据的闭环传输设计，实现数字化恒流输出控制．在R=2.84 Ω，L=25.5 µH匀场线圈负载下，满量程输出响应时间小于18.9 µs，输出纹波峰峰值控制在30 mV，正负电流输出对称性良好，长时间工作最大输出偏差是4.8‰．该电源在采用0.5 T-Halbach构型磁体的磁共振波谱系统中完成匀场实验，驱动一阶匀场线圈完成24.48 ppm（10^-6）到2.72 ppm的磁场均匀度优化．此工作有助于紧凑型磁共振波谱仪系统集成及主动匀场技术相关应用的开展．

关键词: 核磁共振（NMR）, 主动匀场电源, 高精度, 高稳定, 多通道

Abstract:

Highly homogeneous magnetic fields in magnetic resonance spectrometers are an important guarantee for improving the quality of spectra for chemical structure analysis and kinetic information. The active shimming process using a shimming power supply to drive a shimming coil to produce a compensating electromagnetic field is an essential way to improve the homogeneity of the magnetic field. The high accuracy and stability of the shimming power supply’s output are crucial indicators for improving the active shimming capability and maintaining the shimming results. The paper develops a high-precision, high-stability, low-ripple active shimming power supply system for magnetic resonance spectrometers, and designs a shimming current driver (constant current source) with output state monitoring based on negative feedback control, coupled with an MCU control platform and host computer system to complete the closed-loop transmission of control commands and data between hardware and software, to achieve digital constant current output control. Under R=2.84 Ω, L=25.5 µH shimming coil load, the full-scale output response time is less than 18.9 µs, the output ripple peak-to-peak control is 30 mV, the positive and negative current output symmetry is good, and the maximum output deviation is 4.8‰ for long time operation. This power supply was used in a nuclear magnetic resonance spectrometer system using 0.5 T-Halbach configuration magnets, and the magnetic field homogeneity was optimised from 24.48 ppm (10^-6) to 2.72 ppm by driving a first-order shimming coil. This work contributes to the integration of compact nuclear magnetic resonance spectrometer systems and the applications related to active shimming.

Key words: nuclear magnetic resonance, active shimming power supply, high precision, high stability, multi-channel

中图分类号:

O482.53

刘庭伟, 彭博文, 徐雅洁, 王亚, 王峰, 郁朋, 杨晓冬. 一种用于磁共振波谱仪的主动匀场电源设计[J]. 波谱学杂志, 2024, 41(2): 117-127.

LIU Tingwei, PENG Bowen, XU Yajie, WANG Ya, WANG Feng, YU Peng, YANG Xiaodong. A Design of Active Shimming Power Supply for Magnetic Resonance Spectrometers[J]. Chinese Journal of Magnetic Resonance, 2024, 41(2): 117-127.

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序号	T	名称	时间（最小值）/ns
1	t₁	串行时钟周期	33
2	t₂	串行时钟高峰时段	13
3	t₃	串行时钟低谷时段	13
4	t₄	同步时钟到串行时钟上升沿建立时间	0
5	t₅	数据建立时间	5
6	t₆	数据保留时间	4.5
7	t₇	24^th串行时钟下降沿到同步时钟上升沿建立时间	0
8	t₈	最短同步高电平时间	33
9	t₉	24^th串行时钟下降沿到同步时钟下降沿建立时间	100