Study Of Atomic Magnetometer Arrays In Geomagnetic Environments

High-sensitivity Magnetic Anomaly Detection System(MAD)has been of great research significance in basic physics research,industrial nondestructive testing,underwater magnetic obstacle identification,and biomedical detection.For the detection of magnetic anomaly objects,on the one hand,it is necessary to improve the sensitivity of the magnetometer,and at the same time build magnetometer arrays to realize the multi-channel measurement of signals,improve the measurement accuracy,and reduce the measurement error;On the other hand,it is necessary to reduce and compensate the magnetic noise caused by the platform and the environment accordingly,the high-performance magnetometer array combined with the low noise measurement platform and the optimized magnetic anomaly signal algorithm can achieve the precise localization of underwater magnetic obstacles.For the need for more sensitive magnetic anomaly detection,it is important to study active magnetic compensation for magnetic anomaly detection and high-performance magnetometer arrays.In recent years,the rise of quantum sensing technology has provided better possibilities for achieving higher-sensitivity magnetic anomaly detection,especially atomic magnetometers based on light-atom interactions,the most sensitive magnetometers.With the advantages of high sensitivity,easy miniaturization and arraying,atomic magnetometers can be applied to the detection and localization studies of magnetic anomalous objects.In this thesis,we experimentally construct a high-sensitivity atomic magnetometer array in a geomagnetic environment with the goal of achieving highprecision identification of weak magnetic targets in a geomagnetic environment,and investigate the effects of different magnetic compensation methods on reducing magnetic noise and the effects of inelastic wave mixing enhancement methods on magnetometer signal enhancement in a geomagnetic environment.Using the constructed magnetometer array in the geomagnetic environment,we initially obtained the direct detection of magnetic anomaly signals in the experiment.The innovations in this paper are:1.Implementation of atomic magnetometer arrays and detection of magnetic anomaly signals in a geomagnetic environment.Dual-channel and Quad-channel magnetometer arrays were built in the experiments.For the dual-channel atomic magnetometer,the scheme of using one of the optical signals instead of the triaxial fluxgate for magnetic field feedback was experimentally investigated,and higher sensitivity was measured under this condition.A quadchannel atomic magnetometer was built,and the sensitivity of each channel was measured separately.A magnetic anomaly object was placed outside the coil,and the magnetic anomaly signal was observed on the quad-channel atomic magnetometer.2.Magnetic compensation system and non-magnetic heating system for the atomic gas cell were developed.In this paper,a magnetic compensation system was designed using a triaxial fluxgate and PID to suppress the magnetic field fluctuation from±160 nT to±10 nT.To reduce the noise caused by heating,a controllable triggered non-magnetic heating system is designed,and the sensitivity measurement is realized during the heating shutdown process to avoid the influence of electrical heating noise.The temperature control range is 30-150℃,which fluctuates about 0.03℃.3.Single-beam nonlinear magneto-optical rotational magnetometer and inelastic wave mixing enhancement of the rotational signal.The nonlinear magneto-optical rotational signals in a single magnetically shielded environment and a geomagnetic environment are investigated separately.The enhancement of the nonlinear magneto-optical rotational signal by the inelastic wave mixing enhancement scheme is investigated,and the experimental results show that the inelastic wave mixing enhancement scheme can significantly improve the signal intensity and reduce the requirement of the experimental system for detecting the optical field.