基于梯度线圈和双光束反向补偿的NMRG主磁场匀化方法  

Main magnetic field homogenization by gradient coil compensation and double beams with opposite propagation direction for Nuclear Magnetic Resonance Gyroscopes

作　　者：舒强 吉方[2] SHU Qiang;JI Fang(Institute of System Engineering,China academy of engineering physics,Mianyang 621900,China;Institute of Mechanical Manufacturing Technology,China academy of engineering physics,Mianyang 621000,China)

机构地区：[1]中国工程物理研究院总体工程研究所,四川绵阳621900 [2]中国工程物理研究院机械制造工艺研究所,四川绵阳621000

出　　处：《光学技术》2024年第4期391-398,共8页Optical Technique

基　　金：四川省自然科学基金(2022NSFSC0921)。

摘　　要：核磁共振陀螺气室磁场梯度导致的核自旋横向弛豫率是制约陀螺角度随机游走性能提升的重要因素。提出了基于梯度补偿线圈和双光束反向补偿的主磁场匀化方法。建立了气室原子系综Rb电子自旋极化、核自旋极化和泵浦光场传播的多场耦合动力学模型,结合有限元分析方法获得了方形气室磁场梯度与Xe核自旋横向弛豫的量化关系,分别对梯度线圈补偿环境磁场梯度、反向传播双光束均匀泵浦的Rb极化等效磁场匀化方案进行了研究。结果表明:梯度线圈将5×5×5mm^(3)气室的^(129)Xe_(T_(2))由3.6s提升到5.7s;Rb原子极化均匀性在纵向和横向都得到了显著改善,Rb原子极化等效磁场的一阶梯度得到抑制,残留的二阶等效磁场梯度导致的Xe核自旋横向弛豫率降低到约10^(-4)·s^(-1)量级。The magnetic field gradient induced transverse relaxation rate of noble gas atom spins has an important role on the sensitivity of the Nuclear Magnetic Resonance Gyroscope.In order to improve the gyro sensitivity,the magnetic field gradient needs to be suppressed.In addition to the environmental magnetic field gradient,the equivalent magnetic field gradient caused by the polarization inhomogeneity of Rb atoms also exists in the cell of the gyro sensor head.Therefore,a main magnetic field homogenization method based on gradient compensation coil and double beam reverse compensation is proposed.A multi field coupling dynamic model including Rb electron spin polarization,nuclear spin polarization and pumping light field propagation is established.The quantitative relationship between the magnetic field gradient of the cubic cell and the relaxation of Xe nuclear spin is obtained by the finite element analysis method.Through experiments and numerical analysis,the equivalent magnetic field homogenization method by the gradient coil and the reverse propagation double beam uniform pumping is studied.The experimental and numerical results show that T_(2)of ^(129) Xe is improved from 3.6sto 5.7sin a 5×5×5mm^(3) cell and the polarization uniformity of Rb atom has been significantly improved in both longitudinal and transverse directions.The equivalent magnetic field of 1st order has been significantly suppressed,and the lateral spin relaxation rate of Xe nucleus caused by the residual second-order equivalent magnetic field gradient has been reduced to about 10^(-4)·s^(-1).

关 键 词：核磁共振陀螺 磁场梯度 双光束反向补偿 弛豫率 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置]