Study On Magnetic Sensing System Of Cesium Self-oscillated Optically Pumped Magnetometer

Since ancient times,people have never stopped using the magnetic field.Today,the weak magnetic field detection technology has been widely used in various walks life,including biomedical testing,geo-environment investigation,military antisubmarine surveillance and aero-geophysical detection and so on.Magnetic detection technology is also divided into several types based on different principles,among which optically pumped magnetometer(OPM)has features like higher sensitivity and accuracy,relatively simple structure,miniaturization,easier for integration.In this paper,OPM is studied.OPM achieved magnetic field detection based on atomic Zeeman Effect and Optical Pumping Effect and optical-magnetic resonance under weak magnetic environment.According to the different working substance,signal feedback methods,excitation modes,OPM can be divided into several types.In this paper,cesium selfoscillated & RF excited OPM is studied.At present,there are several domestic research institution based on universities has been doing research on magnetometer and some institutes have developed magnetometer product,the performance of which continue to improve.But in terms of sensitivity,precision,miniaturization,there is still a certain gap with the world advanced level.Therefore,there is still room for further development of the weak magnetic detection technology in our country.In this paper,the physical basis of magnetism measurement by OPM is researched.The influence of the optical parameters on population in resonance is analyzed.The optical system and hardware circuit are analyzed,designed and actualized,the system can work normally.Magnetic shielding cylinder is analyzed and calculated,then the effects of the size parameters on magnetic shielding effectiveness is verified by modeling simulation.The main works are as follows:(1)The development history of OPM and research status of the magnetic shielding device is discussed.The physical principle of cesium atomic self-oscillated OPM is theoretically analyzed.Including cesium Zeeman Effect,Optical Pumping Effect and optical-magnetic resonance.the magnetic measurement formula of cesium OPM is derived.The expression of the atomic magnetic moment and the optical signal in resonance is deduced.The effect of optical parameters on variation of the population in resonance is analyzed and verified.(2)Based on the requirement of magnetometer calibration,the design and optimization analysis of OPM magnetic shielding is carried out.The principle of magnetic shielding was theoretically analyzed.The formula of multi-layer magnetic shielding is deduced and modified.The influence of size parameters on magnetic shielding effectiveness is verified by simulation,which provides the basis for designing magnetic shielding.(3)The realization principle of optical system and electrical system,and signal changes of each module are analyzed.According to the performance requirements of each part of the system,optical and electrical parameters are designed and debugged to realize the construction of experimental system.