The Investigation On The Environmental Worthiness Of Portable Cold Atomic Gravimeter

Recently, with the progress of laser cooling & manipulating neutral Atoms, especially the MOT technique and laser stimulated Raman transition technique, it is easy to manipulate the neutral atoms within vacuum chamber. Meanwhile, there are huge demands in Gravity precise measurement instruments among several fields such as Geophysics, Exploration of resources and Navigations. Therefore, due to their simple principle, convenience to operate and high repeatability, the Mach-Zehnder type atomic interferometers based on atomic internal state interference have been developed quickly in these years. The small transportable atom gravimeter developed by our group is based on them. The Gravimeter can be applied for Gravity measurements in the laboratory. However, the real work condition of a Gravimeter is more complex and unstable. So it is necessary to carry out the investigation on the environmental adaptability for a gravimeter. This paper aims to analyze its environmental influence on gravity precise measurement and to investigate its environmental adaptability. Therefore we can give the environmental condition for a cold atom gravimeter which can run normally, eventually enhance the precision of gravity measurement.In this paper we first describe the available background, prospect of mobile gravimeter and advances in research at home and abroad. Then we introduced the basic theoryof the atomgravimeter, including the theory of stimulated Raman transition, the principle of gravity measurement, the process of gravity measuement and the model of noise analysis. The principles and methods of environmental worthiness are also briefly described. We study the environmental adaptability of the gravimeter, and found if the environmental temperature rises up 10℃ in a short time (1～2 hours), the noise levels of gravity measurement will change from 40μGal to 120μGal by order. The corresponding systematic error will change about 2mGal. If the environmental temperature quickly go back to its original level, the noises and systematic errors of gravity measurement could automatically restore to the original level. In addition, we also found that the vertical environmental magnetic fields of several Gausses will produce a systematic error for a gravity measurement, but it can be eliminated by the positive and negative chirp frequency sweep fringe. Finally, we evaluated the influence of system running and different 10MHz reference source on the measurement noise.