The Research Of ~4He Optically Pumped Magnetometer's Signal Detection Technology

The magnetic field measuring technique is an important mean to research the physical phenomena which relates to the magnetic phenomena. At present, in domains like scientific research, national defense development, industrial production and daily life, it is playing the very important role. Therefore, the research and the development of high performance's magnetic field measuring equipments has the profound significance.The optically pumped magnetometer is one kind of magnetic measurement equipment with high sensitivity which developed from the 1950s. It is based on the element atom energy level's zeeman effect in the magnetic field, made with optical pumping action and the magnetic resonance technology. The optically pumped magnetometer can not be ignored in the application prospect of the earth magnetic field measurement aspect. Appears after the proton magnetometer, the optically pumped magnetometer's sensitivity is extremely high, which belong to the high one in all kinds of magnetic field measurement devices put into the application. Based on all sorts of merits, the optically pumped magnetometer aroused universal attention around the world immediately since it has been published. It has been successfully developed to various types of optically pumped magnetic measurement equipment, and now it is in the phase of expanding the use and in-depth exploration.In this paper, we will study how to detect and control the signal of the helium optically pumped magnetometer, the paper elaborates the helium optically pumped magnetometer's atomic physics principle, Simultaneously, it researches the signal detection technology of helium optically pumped magnetometer systematicly. It gives the overall structure diagram for the detection method of fast tracking with the doubled frequency error signal, and analyzes its working principle fully, then designs and produces the detection and control closed-loop system of the helium optically pumped magnetometer. Through the test we get the test data, and illustrate the effectiveness of the system design by analyzing the test results.The full text is divided into six chapters altogether.Chapter one: Mainly introduces the background and the significance of the research, Summarizes the research situation and the development trend of the helium optically pumped magnetometer both domestic and foreign, describes the characteristics of the optically pumped magnetometer, and gives a brief description on the advantages of the resonant element helium(4He).Chapter two: Elaborates the helium optically pumped magnetometer's atomic physics principle, describes the optical system's structure of the probe, and also elaborates the working mechanism of the optical pumping action and the magnetic resonance function.Chapter three: Analysis and comparison of optically pumped helium magnetometer's signal detection method, elaborates the working principles of the traditional detection method and the detection method of fast tracking with the doubled frequency error signal separately, discusses their advantages and disadvantages, and gives the corresponding detection system block diagram of the two detection methods.Chapter four: Design helium optically pumped magnetometer's detection control loop by using the detection method of fast tracking with the doubled frequency error signal, including the analysis and design of each module: the Pre-amplifier, the amplitude controller, the doubled frequency error signal frequency selector, the base frequency modulation signal frequency selector, the phase-sensitive detector, the amplitude discriminator, the strobe controller, the modulation signal generator, the controllable integrator, the voltage-controlled oscillator, the pre-placed frequency divider, the high frequency excitation oscillator, the magnetic field counting unit, the single-chip microcomputer system.Chapter five: Tests the detection and control closed-loop system and analyzes the test results, this chapter with chapter four and five constitute the key part of the thesis together.Chapter six: The full text is summarized, achieves a comprehensive summary of the research work and results in this paper, analyzes the insufficiency, put forward the corresponding proposal for the future work.