氦光泵磁力仪探头设计和环路数字化研究

磁法勘探是一种常用的地球物理勘探方法，其中光泵磁力仪是国内外应用于航空和地面磁法测量最多的磁力仪器.为满足深部矿产资源勘查对高精度磁测设备的需求，本文开展了低噪声、宽量程的高性能数字氦光泵磁力仪关键技术研究，主要包括磁传感器探头优化设计和新型数字化环路设计两方面.首先通过深入分析影响氦光泵磁力仪灵敏度的主要决定因素，对磁传感器关键部件氦灯、氦室进行小型化技术研究，解决高性能氦泵源和原子气室等关键件的制作工艺，提高氦灯效率和氦吸收室的磁共振信号输出强度，制作出高性能、低噪声的小型化氦光泵探头.然后，针对常规模拟跟踪环路的局限性，通过数字化技术研究，采用FPGA、DSP、DDS、环路跟踪算法和信号处理软件等技术构成新型数字环路，弥补现有基于模拟跟踪环路技术的模拟式氦光泵磁力仪的不足，该数字环路降低了氦光泵磁力仪的电路噪声，增强了抗电磁干扰能力，并扩展了磁力仪的量程.本文通过小型探头和数字环路的技术设计，研制出高精度大量程的地面数字氦光泵磁力仪，并用于第三方测试.通过第三方测试证明：实测仪器的静态噪声小于4 pT，磁场测量范围为20000~100000 nT，梯度容限大于10000 nT/m.

Design of helium optical-pumping magnetometer probe and digital loop electronics circuit

Magnetic prospecting is a commonly used geophysical technique, in which the optically pumped magnetometer is the most popular instrument in aerial and ground surveys. To meet the demand of exploration of minerals and resources at depth on high-accuracy magnetic equipment, this work developed low noise, large measure range digitized helium optically pumped magnetometers. We have analyzed main influence factors of sensitivity, and studied the production process of helium lamp, vapor cell, and miniaturized the helium lamp and vapor cell of optically pumped magnetometers. By virtue of this research in technology, the helium lamp efficiency and the intensity of magnetic resonance signal were enhanced, and miniature probes of helium optically pumped magnetometers were fabricated. To solve the limitation of simulative feedback circuits, in terms of study on digitization, FPGA, DSP, DDS, tracking algorithm feedback circuits, and signal process software were used to create innovative digitized feedback circuits. These circuits improve the performance of the helium optically pumped magnetometer, decrease the noise of circuit, avoid the electromagnetic interference and extend the measurement range. Based on the design of the miniature probe and digitized feedback circuits, this work developed digitized a new helium optically pumped magnetometer. Test results show its static noise is less than 4 pT,measurement range is 20000~100000 nT, and gradient tolerance is greater than 10000 nT/m. Field experiments and user response demonstrate that the development of this digitized helium optically pumped magnetometer is successful.