强自旋极化效应的高精度Overhauser磁力仪研究  

Research of a high-precision Overhauser magnetometer based on the strongly polarize nuclear spins effect

作　　者：罗望 胡祥云[1,2] 葛健 刘立超 佘锦华 董浩斌 LUO Wang;HU XiangYun;GE Jian;LIU LiChao;SHE JinHua;DONG HaoBin(School of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China;Hubei Subsurface Multi-scale Imaging Key Laboratory,China University of Geosciences,Wuhan 430074,China;School of Automation,China University of Geosciences,Wuhan 430074,China;TokyoUniversity of Technology,Tokyo 1920982,Japan)

机构地区：[1]中国地质大学(武汉)地球物理与空间信息学院,武汉430074 [2]地球内部多尺度成像湖北省重点实验室,武汉430074 [3]中国地质大学(武汉)自动化学院,武汉430074 [4]Tokyo University of Technology,Tokyo 1920982

出　　处：《地球物理学报》2024年第12期4583-4593,共11页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2023YFF0718000);国家自然科学基金(42374225,42374224,42220104002,42404193);国家博士后科学基金(2023M743294);湖北省自然科学基金计划项目(2024AFB199)联合资助。

摘　　要：Overhauser磁力仪是磁法勘查技术的重要基础仪器,被广泛用于磁场标量数据精度要求较高的地球科学研究、国防安全等领域.传统的Overhauser磁力仪受限于动态核极化效应中电子自旋能量较弱,导致质子系统吸收能量少,输出感应衰减信号(FID,Free Induce Decay)差,使得地磁总场测量精度低.对此,本论文提出引入强自旋极化效应设计新型Overhauser磁力仪,利用重核磁场磁化自由电子,增强自由电子能量,从而提升质子系统磁化强度,改善磁力仪测量精度.论文讨论了适用于地磁测量的强自旋极化Overhauser效应理论架构及其自由基结构,并针对强自旋极化效应的激发与FID信号的测量,设计了新型Overhauser磁力仪的传感器激发部件、信号提取与测频方案,最后实验分析了强自旋极化效应激发参数,并将新型Overhauser磁力仪与传统磁力仪及商用磁力仪进行了性能对比.结果表明,强自旋极化效应可有效改善FID信号幅度,相对传统类Overhauser磁力仪信号幅度增加2.8倍,新型Overhauser的实际测量精度可达0.048 nT,与国际领先商用Overhauser磁力仪相当.The Overhauser magnetometer is an essential instrument in magnetic exploration technology,widely used for high-precision scalar magnetic field data acquisition in Earth science research and national defense.Traditional Overhauser magnetometers face limitations due to the relatively weak electron spin energy in the dynamic nuclear polarization effect,which results in low energy absorption by the proton system,inferior Free Induction Decay(FID)signal output,and consequently,lower accuracy in measuring the total geomagnetic field.In this paper,we propose a novel design for the Overhauser magnetometer by introducing the Strongly Polarize Nuclear Spins(SPNS)effect.The novel design exploits the magnetization of free electrons by the heavy nuclear magnetic field,enhancing the energy of free electrons and thereby improving the magnetization intensity of the proton system to enhance measurement accuracy.First,we discuss the theoretical framework of the SPNS Overhauser effect suitable for geomagnetic measurements and its free radical structure.Subsequently,focusing on the excitation of the SPNS effect and the measurement of FID signals,we detail the design of the sensor excitation structure,signal extraction,and frequency measurement scheme for the novel Overhauser magnetometer.Finally,we experimentally analyzes the parameters of the SPNS effect,comparing the performance of the novel Overhauser magnetometer with traditional and commercially available magnetometers.The results indicate that the SPNS effect effectively improves the amplitude of the FID signal,achieving an approximately 2.8-fold increase in signal amplitude compared to traditional Overhauser magnetometers.The actual measurement accuracy of the novel Overhauser magnetometer can reach 0.048 nT,comparable to internationally leading commercial Overhauser magnetometers.

关 键 词：地磁场测量 Overhauser磁力仪 强自旋极化效应 FID信号 传感器 

分 类 号：P631[天文地球—地质矿产勘探]