Demonstration Of Sub-μGal Resolution Gravity Measurement By Atom Interferometer

The gravitational acceleration is one of the important parameter in gravity field. High precision gravity measurement plays an important role in geophysics, geodesy and fundamental physics. Because of its high sensitivity and the virtue of long time continues measurements, worldwide interest in atom is stimulated. Our laboratory built an atom gravimeter base on simulated Raman transitions since2006. In2011, we achieved a sensitivity of about5.5×10-8g/Hz1/2. The corresponding resolution with a100s integration time is about5.5μGal (lμGal≈10-9g).The primary assignment during my doctoral section is to enhance the sensitivity of gravity measurement based on our previous work. The main works are as follows:①Designed and built a new system, which is similar to our previous one except several changes to improve the performance. A2D-MOT is added to increase the loading rates of3D-MOT and reduce the influence of atom shot noise in detection, a lower noise OPLL is used to reduce the influence of the phase noise of Raman beams, etc.(2) With these efforts, we achieved a short-term sensitivity of about4.2×10-9g/Hz1/2for absolute gravity measurements, which improve the sensitivity by a factor of2comparing to the former best reported value.③Calibration experiment using two attracting masses was carried out to prove the resolution directly, which indicate the resolution of our new gravimeter is better than0.5μGal@100s.④Some noise modulation experiments also indicate that the resolution is not limited by atom shot noise, the residual vibration noise, and the phase noise of Raman beams. The limitation of the residual vibration noise is about0.1μGal@100s, which indicates that we can get a resolution at this level.In this dissertation, the major work especially the improvements of our second system will be described in detail. Some noise modulation experiments are carried out and indicate that the resolution of our gravimeter is mainly limited by detection noise, the frequency noise and intensity noise of the Raman beams. We prospect the future work of gravity measurement at the end.