Design Of Electronics System For Tracking Cesium Atom Laser Magnetometer

Thanks to the rapid development of the field of photophysics,high-precision magnetic field measurement technology has been greatly developed and is widely used in geological survey,mineral exploration,biomagnetic field measurement,military monitoring,magnetic resonance imaging and other fields.As a high-precision magnetic field measuring instrument,helium atomic laser light pump magnetometer has many advantages such as high sensitivity,fast frequency response,high sampling rate and low power consumption.It has become a research hotspot in the field of magnetometers in the world.Compared with foreign developed countries,there still has a large gap in some technical indicators in China's research on optical pump magnetometers,and there are no mature products.Therefore,it is important to study the high-performance index of the Dawn Pump Magnetometer.This paper first introduces the research background and principle of the tracking laser pump magnetometer,and expounds the idea and overall design scheme of the magnetometer electronics system.Secondly,the key technologies in the electronic system and the key technologies in signal processing are discussed in detail.Finally,the paper also analyzes the test methods and test results of the functional modules and the performance of the tracking laser light pump magnetometer.The electronic system of the magnletometer is mainly composed of laser control loop,RF field scanning control loop,and signal detection and processing.The key parts are laser temperature control circuit,high-precision multi-channel coherent signal source and digital lock.Phase processing algorithms,etc.The main research work of the thesis is also reflected in these aspects.The specific research content is as flows:1)The laser temperature control circuit is designed and optimized to achieve the stability of the laser wavelength and improve the sensitivity of the magnetometer.Temperature directly affects the output wavelength of the laser.The stability and control of the laser temperature is one of the key technologies of the magnetometer.Taking the MAX 1978 temperature control chip as the core,it has made a lot of optimizations for its peripheral core components,PID circuit parameters,circuit board layout,laser protection circuit,etc.,achieving temperature control circuit unit with fast temperature control,small size and high safety.After testing,the temperature control unit has a temperature drift of less than 0.003 ? for 11 hours,and the VCSEL wavelength change amount is less than 0.14 pm for 11 hours,and the temperature step is continuously adjustable.2)A multi-channel coherent signal source scheme based on FPGA is proposed,which solves the special requirement of the four-channel coherent signal of the tracking laser optical pump magnetometer,and is small in size and easy to control.The signals are respectively supplied to the scan signal of the RP field scan and the phase-dependent reference signal for demodulation,the control signal supplied to the laser for stabilization,and the phase-dependent reference signal due to the demodulation.The unit is implemented by FPGA-based DDS design scheme.The key FPGA logic design is designed to accurately adjust the phase difference of the signal output,and the frequency is modulated.The appropriate hardware circuit is designed to make the output frequency reach 70KHz-350KHz.0.35mHz.3)A digital phase-locked signal detection scheme is proposed,and a digital phase-locked demodulation algorithm for magnetic resonance signals is designed to achieve accurate measurement of the magnetic field.The core algorithm of digital phase locker and filter is analyzed by MATLAB simulation,and is realized by STM32.The value of the measured magnetic field is obtained by the corresponding Larmor coefficient between the magnetic field signal and the frequency of 3.49857 Hz/nT and the method can demodulate the signal frequency corresponding to the magnetic field to 350KHz.