Chinese Journal of Magnetic Resonance >
Magnetic Field Locking System Based on Fluxgate and Time Domain Digital Frequency Discrimination
Received date: 2022-03-28
Online published: 2022-04-28
The magnet of permanent magnet magnetic resonance instrument is susceptible to the interference of temperature and other environmental magnetic fields, resulting in fluctuations of the main magnetic field, which affects the repeatability and accuracy of the measurement. In this paper, two locking methods to solve the magnetic field fluctuation are discussed. On the one hand, the transient magnetic field caused by environmental fluctuation is detected by fluxgate sensor with high sensitivity, and then the field programmable gate array is used for real-time processing and calculation of the magnetic field compensation. On the other hand, the time-domain digital frequency discrimination locking method is employed for the slow magnetic field drift caused by changes in ambient temperature. After the locked sample being excited by radio frequency, nuclear magnetic resonance (NMR) signal is converted to a lower frequency range through frequency mixing, converted into a square wave signal, and directly sent to the field programmable gate array for periodic measurement. The magnetic field compensation amount is also obtained by calculation. The magnetic field compensation obtained by the two methods is superimposed, and then converted into current signal to drive B0 compensation coil mounted on the magnet, thereby a magnetic field locking system is developed to realize the locking of the magnetic field. The test is carried out on a 0.5 T food rapid detection magnetic resonance analyzer. When subjected to transient interference, the magnetic field can be stabilized within the range of ±4 Hz (corresponding to ±0.093 9 μT), and the magnetic field drift caused by temperature can also be accurately measured, which verifies the feasibility of the magnetic field locking method presented in this paper.
Xiao-yang ZHANG , Shou-quan YAO , Jun-cheng XU , Yu JIANG . Magnetic Field Locking System Based on Fluxgate and Time Domain Digital Frequency Discrimination[J]. Chinese Journal of Magnetic Resonance, 2022 , 39(4) : 448 -458 . DOI: 10.11938/cjmr20222990
| 1 | 成江波. 低场NMR磁体模糊自适应多路PID温控算法的研究及应用[D]. 武汉: 中国科学院精密测量科学与技术创新研究院, 2021. |
| 2 | 马钦忠, 王炜, 龚耀, 等 上海市地铁对地磁观测影响的实验分析[J]. 地震地磁观测与研究, 2004, 25 (5):24-29. |
| 2 | MA Q Z, WANG W, GONG Y, et al Experimental analysis of the influence of subway on geomagnetic observation in Shanghai[J]. Seismological and Geomagnetic Observation and Research, 2004, 25 (5):24-29. |
| 3 | 王洪 排除磁共振成像中交流干扰的方法探讨[J]. 中华放射学杂志, 2001, 35 (11):865-866. |
| 3 | WANG H Study with a method of excluding AC disturbances in MRI[J]. Chinese J Radiol, 2001, 35 (11):865-866. |
| 4 | 李建奇. 磁共振成像中若干方法问题研究[D]. 上海: 华东师范大学, 2010. |
| 5 | 华东师范大学. 校正磁共振成像系统中主磁场不稳定的方法: 中国, 200910047219. 6[P], 2009-08-19. |
| 6 | 杨畅, 陈俊飞, 陈黎, 等 NMR永磁体精密温度控制器的设计与实现[J]. 波谱学杂志, 2018, 35 (3):294-302. |
| 6 | YANG C, CHEN J F, CHEN L, et al Design and Implementation of NMR permanent magnet precision temperature controller[J]. Chinese J Magn Reson, 2018, 35 (3):294-302. |
| 7 | CARLO V, AUGUSTA C, GERARDO P Quantitative 2H NMR spectroscopy with 1H lock extender[J]. J Magn Reson, 2007, 187 (1):120-125. |
| 8 | SOGHOMONIAN V, SABO M, POWELL A, et al Identification and minimization of sources of temporal instabilities in high field (> 23 T) resistive magnets[J]. Rev Sci Instrum, 2000, 71 (7):2882-2889. |
| 9 | KAZIMIERCZUK K, WIKTOR K Efficient compensation of low-frequency magnetic field disturbances in NMR with fluxgate sensors[J]. J Magn Reson, 2005, 174 (2):287-291. |
| 10 | 姚远. 弱磁场的检测与应用技术研究[D]. 武汉: 武汉理工大学, 2002. |
| 11 | 涂传宾. 基于磁通门传感器的微弱磁场检测技术研究[D]. 沈阳: 沈阳工业大学, 2013. |
| 12 | HOU D, WU J T, REN Q S, et al Analysis of long-term phase-locking technique for mode-locked laser with PID regulator[J]. IEEE J Quantum Electron, 2012, 48 (7):839-846. |
| 13 | 蒋焕文, 孙续 电子测量[M]. 北京: 中国计量出版社, 1994. |
| 14 | 梁文海, 秦爽 时频测量技术及应用[M]. 北京: 科学出版社, 2018. |
| 15 | 冯涛, 陈俊飞, 张震, 等 低场核磁共振短死时间射频线圈与射频开关的设计[J]. 波谱学杂志, 2021, 38 (1):1-11. |
| 15 | FENG T, CHEN J F, ZHANG Z, et al A design of short dead-time RF coil and RF switch for low-field NMR[J]. Chinese J Magn Reson, 2021, 38 (1):1-11. |
| 16 | 马聪伟, 杨鸿毅, 钟凯 高场磁共振成像1H/31P双调谐射频线圈研究进展[J]. 波谱学杂志, 2021, 38 (1):118-139. |
| 16 | MA C W, YANG H Y, ZHONG K Research progresses of high-field MRI 1H/31P dual-tuned radio frequency coil[J]. Chinese J Magn Reson, 2021, 38 (1):118-139. |
/
| 〈 |
|
〉 |