Design Of Atom-interferometry Based G Measurement And Experimental Study On Key Technique

The Newtonian gravitational constant G is a fundamental physical constant,which plays an important role in theories of gravitation,cosmology and astrophysics.Howev-er,due to the weakness and un-shielding characteristic of the gravitational interaction,the precise determination of G is very difficult.Since the first G measurement conducted by Cavendish in laboratory in 1798,about three hundred G measuring experiments have been performed.But the uncertainty of G value in CODATA 2018 is only 22 ppm(1 ppm=10^-6),which is the most unprecise one among fundamental physical constants.Moreover,the measurement results from different groups are not consistent within the confidence interval-s.This is most likely to be caused by unknown systematic errors.Our lab has dedicated to G measurement with torsion balance of high sensitivity since 1980s.In 2018,two independent approaches were realized in the same laboratory.Measuring G with independent methods,is helpful to explore and discover possible hidden systematic errors.With this concern,we continue to measure G with atom interferometry,which contribute to another independent approach.In this thesis,we introduce our G measurement scheme and the developmen-t of the key technique,namely the dual-magneto-optical-trap atom interferometry gravity gradiometer,in detail.The main content and results are in three aspects.(1)Design of the atom-interferometry based G measurement,including the scheme of atom interferometry gravity gradiometer and the source masses system.For the design of the gradiometer,an innovative scheme of dual magneto-optic trap is proposed for G measurements,which is not only beneficial to fast loading and launching of atoms,but also beneficial to optimization of the positions of atomic clouds and source masses.For the source masses,tungsten alloy spheres are explored to generate the required addition gravitational acceleration,which takes advantage of good machinability and immunity to density inhomogeneity.(2)Analysis of main systematic errors for atom-interferometry based G measure-ments.Related systematic errors for G measurements by atom interferometry are theo-retically analyzed,and numerical simulation is implemented.Based on the analysis,the positions of the two atomic clouds and the positions of the source masses in the far configu-ration are optimized.The effects of position deviations of the clouds and the source masses on G measurements are estimated.During the analysis,an error related to Raman pulse duration overlooked by other groups is found to be not negligible,and is estimated here.(3)Realization of high precision atom interferometry gravity gradiometer using dual magneto-optic traps.Based on the design,the atom gradiometer has been built up,including the vacuum system,optics system and electronic system.The experiments of atom loading,launching,atom interference and detection are implemented.After the optimization of light shift,compensation of Coriolis effect and suppression of vibration noise,dual-fringes lock is realized for the atom interferometry gravity gradiometer.And a short-term sensitivity of 99 E/(?)(1E=10^-9s^-2)for the gradiometer is achieved,which is at the same level with92 E/(?) in Tino's group,with witch the best G measurement so far is achieved.In the thesis,the work during my doctoral candidate period on atom-interferometry based G measurement described above is presented in detail.This work paves the road to our first stage atom-interferometry based G measurement with an aimed precision of 100ppm.