Research On Key Technology Of New Type Vector Atomic Magnetometer

The magnetic field has attracted much attention as a basic physical concept.Its measurement technology has been widely used in the fields of biomedicine,space and aerospace and military affairs.The cesium atom optical pump magnetometer has been paid more and more attention in the field of magnetic field measurement because of its high sensitivity,small size,and low power consumption.Compared with the traditional magnetometer,the new vector cesium atom magnetometer can measure the direction of the magnetic field and is easier to sense the change of the magnetic field.At present,most domestic atomic magnetometers stay on scalar magnetometers,and the research on vector atomic magnetometers is in the stage of theoretical exploration.This article will carry out research on the key technologies for realizing new vector atomic magnetometers.In this paper,based on the theory of a new type of linearly polarized atomic vector magnetometer,a method for detecting the size and direction of the magnetic field is proposed.Design related experiments to verify the correctness and feasibility of the method,realize the calculation of the magnetic vector,and obtain the magnitude and direction of the vector magnetic field.Another research work is to design a DDS coherent signal source,a broadband lock-in amplifier module and magnetic vector solving related software,which lays the foundation for the realization of a new type of vector atomic magnetic measurement of small instruments.The specific content is as follows:(1)Based on the basic principles of the new vector atomic magnetometer,through the analysis of magnetic resonance signals,a measurement plan for the magnitude and direction of the vector magnetic field is proposed and related physical experiments are designed to verify the feasibility of the measurement plan.(2)Design the DDS coherent signal generator module based on FPGA to realize the simultaneous output of sine wave scanning coherent signal with center frequency f and 2f,which can be used as RF field excitation signal and the reference signal of broadband lock-in amplifier to realize the coherent detection of the signal.The power consumption of this module is 0.75W,and the volume is 16cm×10cm×1cm.(3)Design a broadband lock-in amplifier module to achieve simultaneous demodulation of the first harmonic component and the second harmonic component in the weak magnetic resonance peak signal.In the case of a SNR of 1:10,the broadband lock-in amplifier module can detect weak signals with the frequency of 70kHz～700kHz and the amplitude of 80μV.The error is within 0.7%,the power consumption is 0.425W,and the volume is only 7cm×6cm×2cm,which meets the application requirements of the vector atomic magnetometer.(4)Design related software to realize the magnetic vector calculation of the new vector atomic magnetometer.First,scan the frequency of the DDS coherent signal generator to find the magnetic resonance peak to obtain the Larmor precession frequency,and then use PID to accurately track and lock the Larmor precession frequency to measure the magnitude of the vector magnetic field.Second,the first harmonic and the second harmonic demodulated by the broadband lock-in amplifier are sampled by AD and then fitted to calculate the direction of the vector magnetic field.The test results of magnetic fields with three known directions of 30°,45° and 75°show that the standard deviation of the magnetic field size measurement is less than 60pT,the γ angle standard deviation is less than 0.5°,and the sensitivity is about 3.6pT/(?),which preliminarily realizes the vector measurement of the magnetic field.