Study On The Three-axis Atomic Magnetometer In Nuclear Magnetic Resonance Gyroscopes

Inertial navigation system(INS)is a self-contained navigation system without the need for external references and is not susceptible to external interference.In specific environment(such as the caves and deep ocean),where the satellite navigation system can't function well,it can still achieve the precise navigation of the carrier.As one of the key components of inertial navigation and inertial measurement,the gyroscope is widely used in aviation,aerospace,navigation and other military and civil fields.Because of the advantages of high precision,small size,low cost and insensitive to acceleration,the nuclear magnetic resonance gyroscope(NMRG)has become a new research hotspot in inertial navigation field.The three-axis atomic magnetometer in NMRG has the capability to detect undesired stray magnetic fields,whose magnetic field measurement sensitivity is of great significance for improving the performance of NMRG.Firstly,the operating principle of NMRG,including the physical processes such as Larmor precession,optical pumping polarization,nuclear magnetic resonance and precession frequency detection,is introduced.Secondly,to satisfy the miniaturization demand of NMRG,the three-axis atomic magnetometer for the NMRG is demonstrated.Magnetic field sensitivities of 100f T/Hz^1/2 in x and y axes and 20 f T/Hz^1/2 in the z axis are achieved.The bandwidths of this magnetometer are 96 Hz in x and y axes and 6 Hz in the z axis.Thirdly,the relaxation time of alkali-metal atoms is measured by the transverse atomic magnetometer,while the relaxation time of noble gas atoms is measured by the longitudinal atomic magnetometer.This is conducive to the study on the interaction mechanism of atoms with lasers,atoms,and magnetic fields in the cell,which has great guiding significance for optimizing the performance of the gyroscope.Finally,the closed-loop principle of the NMRG and the performance evaluation method of gyroscopes are introduced.The theoretical analysis on the optimization of performance parameters of the NMRG is presented.After optimizing the parameters of probe light detuning,pump light detuning,static magnetic field size,oscillating magnetic field amplitude and the cell temperature,the optimum analog rotation signal and optimum nuclear magnetic resonance signal of NMRG are obtained.The frequency closed-loop locking of NMRG using single isotope(¹²⁹Xe)is realized,and the angle random walk(ARW)and bias stability of the NMRG are predicted as 0.17°/h^1/2 and 0.33°/h,respectively.When there is magnetic field noise interference,two isotopes are needed to eliminate the magnetic field interference,so that the gyroscope's output is only related to the carrier's angular velocity.By replacing the cell and optimizing the experimental conditions,the frequency closed-loop locking of NMRG using dual isotopes(¹²⁹Xe/¹³¹Xe)is realized,and the angle random walk and bias stability of the NMRG are predicted as 0.92°/h^1/2 and 7.71°/h,respectively.