Investigation Of Cesium Atomic Magnetometer Based On Bell-Bloom Configuration And Circular Dichroism Detection

The techniques of high precision measurement of magnetic field have been wide used in mineral exploration,geological disaster warning,biomedicine and fundamental physics.Among the variant techniques of magnetic field measurement,atomic magnetometers which developed in recent ten years have the highest sensitivity.In this paper,we propose a scheme of Cesium atomic magnetometer based on Bell-Bloom configuration and circular dichroism detection.During this work,we mainly investigate the following contents.(1)The application background of high precision measurement of magnetic field is introduced.The history of quantum magnetometers is reviewed.The development of atomic magnetometers in and abroad is introduced detailed.On this basis,we summarize the development trend of atomic magnetometers.(2)A scheme of Cesium atomic magnetometer based on Bell-Bloom configuration and circular dichroism detection is proposed.The spin polarization of Cesium caused by optical pumping and the process of circular dichroism detection are analyzed theoretically.The theoretical response model of Cesium atomic magnetometer is set up.(3)The laser frequency stabilization method based on linear magneto-optical effects is investigated in theoretical and experimental.The characteristics of frequency deviation at zero point are studied under different angles.This method provides a reference of off-resonant laser stabilization.It can avoid manmade dithering because of its no extra modulation.(4)We design the overall scheme of Cesium atomic magnetometer and the specific physical system structure.The physical system of Cs atomic magnetometer is built successfully.The composition of the physical system is studied detailed.We manufacture the hot air heating system and monitored the cell temperature by fiber grating.After completing the development and testing work of each part of the system,we finally build the physical system of Cs atomic magnetometer.(5)The related parameters of the cesium atomic magnetometer physical system are analyzed in the paper and the proper parameters are finally obtained.After analyzing the frequency response characteristic and magnetometric sensitivity of this physical system,it is found that the sensitivity of the cesium atomic magnetometer physical system has achieved a level of 0.1 pT/Hz1/2 at 100 nT.The parameters affecting magnetometer performance,such as laser frequency,laser intensity,laser beam spot size and the modulation wave are also studied in detail.(6)We finished the development of the closed-loop system with its actual test for this atomic magnetometer.The time-domain peak-peak jitter of this closed-loop system is within 3 pT in one minute of continuous measurement of a constant magnetic field,which changes to 9 pT while in an hour of continuous measurement.The sensitivity of the closed-loop magnetometer system reaches 0.12 pT/Hz1/2,and its 3 dB response bandwidth is about 1.2 Hz.During this project,some innovative results have been obtained:(1)Based on the method of laser intensity modulation and circular dichroism detection and detailed derivation of the process of polarization,detection and relaxation,a complete theoretical model of Bell-Bloom magnetometer is established.The theoretical response spectrum is simulated.(2)The open-loop system of Cs atomic magnetometer based on Bell-Bloom configuration and circular dichroism detection is built successfully.A magnetometric sensitivity of 0.1 pT/Hz1/2 of the atomic magnetometer physical system is achieved at 40 ?.(3)The related parameters of the cesium atomic magnetometer physical system are analyzed.The proper parameters are finally obtained and applied to the actual measurement system.(4)The closed-loop system for this atomic magnetometer is finished.A complete and automatic measurement Cs atomic magnetometer is suceessfully developed.The time-domain peak-peak jitter is within 3 pT in one minute of continuous measurement of a constant magnetic field,which becomes 9 pT while in an hour of continuous measurement.The closed-loop magnetometer system reaches a sensitivity of 0.12 pT/Hz1/2 and its 3 dB response bandwidth is about 1.2 Hz.