Experimental Demonstration Of An Atom Interferometry Gravimeter

The local gravity acceleration g is a key parameter for describing the earth's gravity field, while the accuracy of g measurement is dependent on the absolute gravimeters. In recent years, atom interferometry gravimeters have been proved to be a useful tool for absolute gravity measurements. Because of its high potential sensitivity, we are trying to develop a cold atom gravimeter in our cave lab for precision gravity measurements and gravitational experiments.The cold atom gravimeter is based on the atom interferometry technology by coherently driving the free-falling cold atoms with phase locked Raman beams. By compensating the g induced phase with the well controlled Raman lasers'phase in an atom interferometer, we can find the center of the interferometry fringe, and then get the absolute value of g precisely. In order to experimentally realize an atom inrerferometry gravimeter, cold atoms were prepared in a magnetic-optical trap, launched upward to form an atom fountain, and then coherently manipulated by theπ/2-π-π/2 Raman pulses to obtain an atom interferometry fringe, while the local gravity was deduced from the interference signal.The experimental setup of atom fountain, the phase locked Raman lasers and the primary results of gravity measurement with our atom gravimeter are presented in this thesis, which shows that:1) about 108 atoms with temperature of 7μK have been launched to a height of lm by the cold atom fountain; 2) Raman lasers with low phase noise of-90dBc/Hz between 100Hz to 100kHz are realized; 3) the resolution of the atom gravimeter is 6×10-9g within 203s integration time, and 8 days earth-solid-tide data was also recorded by our gravimeter.In order to improve the resolution of this gravimeter, we have analyzed the influences of many possible noise sources. It shows that the sensitivity of our gravimeter is currently limited by the seismic noise. In addition, we have experimentally demonstrated that the magnetic field sensitive atom interferometer could be used to precisely map the magnetic field in vacuum, and this method is useful in correcting the systematic error due to magnetic field inhomogeneity in an atom gravimeter.