Precision Measurement Based On The Thermal Atomic Ensemble

Thermal atomic ensemble is an important research foundation in the field of precision mea-surement.The precision measurement devices based on thermal atomic ensemble include atomic magnetometer and atomic spin gyroscope.The polarized atomic spins process about the exter-nal magnetic field,and the precession frequency depends on the external magnetic field.The atomic magnetometer measures the magnetic field through detecting the precession frequency of atomic spins.So far,the atomic magnetometer has the highest sensitivity theoretically and exper-imentally.Atomic spin gyroscope also measures the angular velocity via the detecting precession frequency of atomic spin.The precession frequency includes the Larmor precession frequency and angular velocity of the carrier with the known Larmor precession frequency,the angular velocity of the carrier will be deduced from the observed frequency.The atomic spin gyroscope has the advantages of high precision,simple structure,and small size,which make it an important devel-opment direction in the field of inertial navigation in the future.Besides,we have demonstrated a prototype of rotation sensor based on alkali-metal vapor cell.This rotation sensor measures the angular displacement continuously,then the angular velocity and angular acceleration will be deduced through the displacement measurement.This rotation sensor can be used to observe the high-speed rotation of engines in real-time,and monitor the rotation stability of engines.We have studied the influence factors of the signal amplitude,including the temperature and the mag-netic fields.The optimal operating conditions are obtained.Our work provides the possibility of developing rotation sensors based on atomic vapor cell with the advantages of high-accuracy,compactness and low cost.This paper consists of seven chapters.The first chapter is the introduction,which mainly summarizes the previous research about atomic magnetometer,atomic spin gyroscope and angle measurement device.The second chapter introduces the basic physical principle of the precise measurement based on thermal atomic ensemble,including the energy structure of the alkali metal atoms,and the interaction between alkali metal atoms and light.In the third chapter,we introduce the experimental setup,including the optical part,the atomic vapor cell,the control system of the magnetic fields,the magnetic shield system,and the heating system.The optical part includes the pump and probe laser.The technique of saturated absorption spectrum is used to stabilize the frequency of the laser and the acousto-optic modulator is used to stabilize the power of the laser.The vapor cell consists of alkali metal Rb,noble gas,buffer gas,and quenching gas.The Thorlabs current sources are used to control the magnetic fields through the coils.The material of the magnetic shield is permalloy.The heating system uses film resistance to heat the cell.In the fourth chapter,we present an angle measurement device based on alkaili metal vapor cell.A linearly polarized light pass through a quarter wave plate fixed on the test object.The polarization of the light will change if the object rotates.The absorption of light depends on the polarization.By measuring the transmission intensity,the angle displacement and angular velocity of the test object will be deduced.So far,the sensitivity of this angle measurement device is 1 ×10-5o/(?).In the fifth chapter,we introduce the atomic magnetometer,including Bell-Bloom magnetometer,radio frequency magnetometer,and parametric oscillation magnetometer.For all these three kinds of magnetometer,the sensitivity we obtained is in the order of pT/(?).In the sixth chapter,we introduce the basic principle of nuclear magnetic resonance(NMR)gyroscope.We proposed a real-time feedback mechanism to manipulate the nuclear spins,and gives the numerical simulation results,proving the validity of this feedback mechanism.In addition,the close-loop measurement of gyroscope has been achieved.For the close-loop NMR gyroscope,the sensitivity of 3°/(?)is obtained,the bias stability is 10°/h.The seventh chapter summarizes the work of the whole paper,and the future prospects,then put forward some new research problems.