DOE OSTI2011
For the emergency response (ER) and treaty verification communities, methods to determine and/or verify the masses present in containers are highly desirable. Additionally, the ability to perform these measurements passively and rapidly is also important in the ER community. The ability to quantify relevant masses and aspects of their spatial distribution is essential for setting lower bounds in relevant ER calculations and for monitoring treaty compliance. The purpose of this feasibility study was to demonstrate a completely passive, rapid method to determine the mass of high-density material present in a closed box, without the need to move, radiograph, or otherwise manipulate the box. Our method applies an existing, DARPA-AOSense, Inc. developed gravity gradiometer based on atomic fountain interferometer technology originally invented by Steven Chu and his team at Stanford, to perform differential gravity measurements, taken from positions around the container with the heavy mass sources inside. In this feasibility study, done with the AOSense gradiometer, we (equivalently) carried out the measurements by moving the mass source, in the required arrangements and orientations, parallel to the atomic fountain axis. We also built and applied computational models of the atomic fountain responses to our high-density mass sources and the background container to enable the blind determination of the overall masses and configurations of material present in the container in our experiments.