Research On Alkali Metal Cell Based On Ultra-sensitive Atomic Spin Inerital Measurement Device

With the development of quantum technology in recent years,a novel gyroscope based on the effect of atomic spin has became one of the hotspots among traditional gyroscopes,such as mechanical gyroscope,optical gyroscope,and MEMS gyroscope.Under the regime of spin-exchange-relaxation-free(SERF),the spin relaxation time,coherence time,and relevant density of atoms are enhanced.It has a great effect on improving the signal to noise ratio,which provides favorable conditions for atomic spin gyroscope to become the next generation of high-precision gyroscope.As a sensitive header of the atomic spin gyroscope,alkali metal cell determines the sensitivity of the equipment.Research on alkali metal cell based on ultra-sensitive atomic spin inerital measurement device has been carried out.It includes following contents,such as mechanism analysis and modeling of ultra-sensitive SERF atomic spin inertial measurement device(ASIMD),optical properties of alkali metal cell,ratio control and detection of atoms inside the alkali metal cell,and relaxations of atoms.To analyze the principle of ASIMD,the dynamic models of magnetic field measurement based on SERF and process of hyperpolarizing noble gas have been established.The process of hyperpolarizing noble gas has been analyzed in theory and experiments.One method of testing the gyromagnetic ratio of noble gas has been presented,which has been also verified the different noble gases successfully,such as 3-helium,21-neon and 129-xenon.In additional,the magnetization field produced by hyperpolarized noble gas can be detected by SERF atomic magnetometer.To solve the problem of heat distribution in the alkali metal cell,a non-contact method of measuring optical depth theory has been put forward.The method can be used to measure the heat distribution inside the cell successfully,and the thermal equilibrium of alkali vapor inside the cell can also be measured.After improving the layout of the oven,repeated measurements have been carried out based on this method.The relevant thermal equilibrium time is decreased by approximately 10 minutes.The method provides a way for improving the structure of the oven's layout and determining the thermal equilibrium time.To solve the problem of measuring the optical parameters of alkali metal cell under non-destructive measurement,based on the principle of equal inclination interference,a multi-channel cross-modulation method for determining the thickness and refractive index of the alkali metal cell is proposed.In this method,the measurement signal is modulated by a square wave and the modulation signal is demodulated by a reference signal.The method can improve the signal to noise ratio effectively relative to the normal of equal inclination interference method.Measurement errors of wall thickness and refractive index are decreased from the previous 6.9%and 2.6%down to 0.6%and 0.14%,respectively.To measure the mole ratio for alkali metal mixture in cell,a non-contact method of spectral absorption has been used to determine the mole ratio of alkali metal mixture.An equipment for monitoring the mole ratio of alkali metal mixture in cell has been designed.The method provides a way for detecting the relevant mole ratio of alkali metal mixture,and the measurement error is less than 10%.To control and measure gas components in cell,a method based on pressure difference has been used to control the components of different gases.The components of gases can also be measured by spectral absorption of alkali metal in the gases.The method provides a way for detecting the relevant components of gases in cell.To analyze the dynamic response of ASIMD under the external magnetic field,time domain analysis methods have been used to analyze dynamic response of atomic ensemble,such as transient response and steady-state response.The control theory and atomic physics are combined together to analyze the response of the atomic ensemble.The damping ratio,free-running frequency and other parameters of the ensemble have been analyzed under different external magnetic fields.Determination of steady-state basis has been presented.Finally,the performance test for ASIMD improved through the methods mentioned above was performed.A measurement sensitivity of 3.77×10-5°/s/Hz1/2 and a bias stability of 0.23°/h were achieved.