Shielded SNM Detection with Gravity Gradiometry

We propose to develop a cold-atom gravity gradiometer for nonintrusive, passive detection of shielded special nuclear material (SNM) inside a human occupied vehicle. Both SNM and SNM shielding consist of high-Z materials that are substantially denser than background. Previous theoretical studies have demonstrated the efficacy of gravity tomography for identification of shielded SNM. The proposed gravity detection approach is completely passive and safe to vehicle occupants. Furthermore, gravity detection of SNM is complementary to existing radiation detection methods. The fidelity of gravity detection improves with thicker SNM shielding. The proposed highly sensitive, stable, and fieldable gravity gradiometer will measure minute gravity field fluctuations to detect shielded SNM rapidly and with high detection fidelity. In Phase I, we will design and test key components of the gravity sensor. We will complete sensor subsystem build and integration in Phase II. Gravity gradiometer laboratory and field testing will follow in Phase III of the proposed project. The gravity gradiometer proposed for shielded SNM detection has numerous commercial applications: airborne gravity survey for mineral and oil prospecting, ground-based surveys to monitor water tables, and gravity-compensated inertial navigation. Compared to existing state-of-the-art gravity gradiometers, cold-atom sensors offer substantially improved stability, sensitivity, and SWaP at reduced complexity and cost.