激光偏振态调制的Bell-Bloom光泵磁力仪及其梯度仪的研究

发布时间：2018-07-25 12:05

【摘要】：磁场广泛存在于我们周围的空间中。磁场的精密测量在多个领域有着非常重要的应用,如地质勘探、军事导航、医学诊断和工业制造等。因此高精度的磁场测量技术成为了国内外学术界的重点研究方向之一。随着原子物理与激光技术的发展,近十年来高精度原子磁力仪的研究得到了快速的发展。光泵磁力仪是一种高灵敏度与高精度的原子磁力仪。在本文工作中,我们研制了一台用于弱磁探测的Rb原子Bell-Bloom光泵磁力仪(以下简称BB光泵磁力仪)。BB光泵磁力仪不需要射频场的激励,而是基于激光光源的调制来激发磁共振,因而在多通道磁探测器与梯度仪的研究中具有独特的优势。通过研究对比,我们发现对激光偏振态的调制获得信号灵敏度优于对激光频率或幅度的调制。为了适合于无磁屏蔽环境的应用,我们还研制了基于上述方案的磁场梯度仪,并对其性能进行了研究与分析。本论文的第一章阐述了磁场测量的意义,介绍与对比了几种原子磁力仪的测磁原理及特点,并分析了目前磁力仪的发展趋势。第二章主要阐述了BB光泵磁力仪的测磁原理,包括Rb原子的能级结构与塞曼效应、光泵浦效应以及BB光泵的光磁共振原理等。第三章详细介绍了激光偏振态调制的BB光泵磁力仪的实验装置,包括光源部分,磁传感部分以及信号探测部分,用该磁力仪系统分别测量了0.5nT、0.2nT、0.1 nT以及0.05nT的磁场台阶信号,分析了磁力仪的分辨能力。通过分析磁场信号的噪声功率谱,在10Hz处磁力仪获得了2pT/Hz1/2的灵敏度。此外,用优化后的系统分别测量了频率为1Hz、2Hz、5Hz,幅度为400pT的模拟心磁信号,并对原始输出信号做平均后的结果进行了比较。第四章介绍了由双路BB光泵磁力仪组成的磁场梯度仪的实验装置,介绍了在无磁屏蔽环境下,测量了由反亥姆赫兹线圈提供不同磁场梯度时,梯度仪测得的实验结果。最后一章进行了总结,并对该原子磁力仪系统的改进与发展进行了展望。
[Abstract]:Magnetic fields are widespread in the space around us. The precision measurement of magnetic field has important applications in many fields, such as geological exploration, military navigation, medical diagnosis and industrial manufacture. Therefore, high-precision magnetic field measurement technology has become one of the most important research directions in academic circles at home and abroad. With the development of atomic physics and laser technology, the research of high precision atomic magnetometer has been developed rapidly in recent ten years. Optical pump magnetometer is an atomic magnetometer with high sensitivity and precision. In this work, we have developed a RB atom Bell-Bloom optical pump magnetometer (hereinafter referred to as BB optical pump magnetometer) for weak magnetic field detection. The BB optical pump magnetometer does not need the excitation of RF field, but based on the modulation of laser light source to excite magnetic resonance. Therefore, it has a unique advantage in the research of multichannel magnetic detectors and gradiometers. By comparison, we find that the signal sensitivity of laser polarization modulation is better than that of laser frequency or amplitude modulation. In order to be suitable for the application of non-magnetic shielding environment, a magnetic gradiometer based on the above scheme is developed, and its performance is studied and analyzed. In the first chapter of this paper, the significance of magnetic field measurement is described, the principle and characteristics of several atomic magnetometers are introduced and compared, and the development trend of magnetometers is analyzed. In the second chapter, the magnetic principle of BB optical pump magnetometer is introduced, including the energy level structure and Zeeman effect of RB atom, the optical pump effect and the principle of optical magnetic resonance of BB optical pump. In the third chapter, the experimental equipment of the laser polarization modulated BB light pump magnetometer is introduced in detail, including the light source, the magnetic sensing part and the signal detection part. The magnetic field step signals of 0.5nT 0.2nT 0.1nT and 0.05nT are measured by this magnetometer system, respectively. The resolution ability of magnetometer is analyzed. By analyzing the noise power spectrum of magnetic field signal, the sensitivity of 2pT/Hz1/2 is obtained by magnetometer at 10Hz. In addition, the simulated cardiomagnetic signals with a frequency of 1 Hz ~ (2) Hz ~ (2) Hz ~ (5) Hz and an amplitude of 400pT are measured by the optimized system, and the results of the original output signals are compared. In chapter 4, the experimental device of the magnetic field gradiometer composed of double channel BB light pump magnetometer is introduced. The experimental results obtained by the gradiometer when the magnetic field gradient is provided by the anti-Helmhertz coil under the unshielded environment are introduced. In the last chapter, the improvement and development of the atomic magnetometer system are prospected.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24

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