Gravity gradient survey with a mobile atom interferometer

The field of atom interferometry has grown rapidly over the last two decades, opening up a new direction in precision metrology. Atom interferometers have proven to be valuable tools for measuring gravitational and inertial effects. In particular, gravimeters, gradiometers, and gyroscopes based on atom interferometry have all demonstrated high accuracies competitive with state-of-the-art commercial technology. We describe here the development and operation of a compact mobile gravity gradiometer using pi/2 - pi - pi/2 sequence with two-photon stimulated Raman transitions in a dual atomic fountain setup for precision gravity gradient survey and other gravity tests. Various noise sources have been identified and overcome, and a differential acceleration sensitivity of 4.2 x 10-9g/ Hz has been achieved over a 70 cm baseline in the laboratory. The apparatus was then moved into a box-truck and a gravity gradient survey was conducted near a 4 story-deep building, at an accuracy of 7 x 10-9/s 2 in gravity gradient with about three minutes integration at each survey point. The survey results agreed with a theoretical model considering detailed floor plan and building structure. In addition, technique to measure absolute gravity gradient is discussed. Finally, a complete dynamic model of the pi/2 - pi - pi/2 sequence was established, and potential algorithms to de-correlate apparatus platform noise during survey based on this model were identified.