| Newtonian gravitational constant G is a very important basic physical constant.Ob-taining the G value with high precision is of great significance in astrophysics,geophysics,and metrology,as well as deepening our understanding of the theory of gravity.At present,G remains the most imprecise fundamental physical constant known.Atom interferometry is new method for measuring G in recent years which uses the atom-interferometer gravity gradiometer to measure the gravitational effect of the atoms induced by the source masses,and then calculates the G value.This method has great potential in further improving the accuracy of measuring G.Currently,the best result for measuring G with atom interferom-etry reached a total relative uncertainty of 148 ppm(1 ppm=10-6).The improvement of measuring G with the atomic interferometry method is significantly limited by the posi-tioning accuracy of the source masses,and the measurement accuracy of the atomic initial conditions.Therefore,how to reduce the systematic errors through the scheme design,so as to achieve high-precision measurement of the G value has important research significance.In addition,the atom-interferometer gravity gradiometer is an important tool for measur-ing G,and a perfect theoretical model for it can provide a certain theoretical reference for measuring G with high precision.This paper mainly focuses on the scheme design and theoretical modeling of the G measurement by the atom interferometer.The main research contents are as follows:（1）Exploration of a new scheme for measuring Newtonian gravitational constant based on the atom-interferometer gravity gradiometer.In the atomic interferometry experiment,the positioning uncertainty of the source masses and the uncertainty of the atomic initial conditions affect the measurement result by coupling themselves with the gravitational gradient,thus affecting the measurement accuracy of G.Based on the phenomenon that“Uniform gravitational field produced by an infinite plate with uniform mass density,and the gravitation of the spherical shell with uniform mass distribution to any spherical interior point is equal to zero”,we design specially the material,geometry and the positions in the close and far configurations of the source masses,in which a nearly uniform gravitational field in the interference region of the atom clouds is constructed.This design can greatly weaken the coupling effect of the uncertainties of the atomic initial conditions with the gravitational gradient induced by the source masses.By properly designing the parameters of the source mass,the atom cloud and the laser,a scheme for measuring G with a relative standard uncertainty of 27 ppm is proposed.（2）Theoretical modeling of the atom-interferometer gravity gradiometer and the exploration of the error suppression scheme.Generally,the G measurement is based on the gravity gradiometer composed of two three-pulse atom interferometers with a sequences.In principle,one four-pulse atom interferometer can also be used for gradient measurement,and then the G value can be measured by using the source masses to carry out position modulation in close-far configurations.For this reason,a better vector model of the four-pulse atom interferometer is established by using the evolution operator method,which considers the effects of laser detuning,pulse duration,gravity gradient,AC-Stark frequency shift,atomic initial velocity and the Earth’s rotation.This universal model can be applied to both gradient measurement and rotational measurement.In addition,aiming at the coupling effect of large laser detuning and pulse duration,as well as the coupling effect of Earth’s rotation,atomic initial velocity and pulse duration,an improved pulse sequence suppression scheme is proposed. |
