M.R. Sternat, J.C. Ragusa, W. Bangerth, “Optically Thick Heterogeneous Object Imaging Using Constrained Optimization and Diffusion Theory”, Poster presented at the Academic Research Initiative Grantees Conference, Washington, D.C., April 6-9, 2009.
In the field of nuclear and global security, smuggling of special nuclear materials by transportation in containers on boats poses strong threat of special interest. To prevent this possible smuggling pathway, a detection system must be implemented that will have the ability to detect high enriched uranium (HEU) where current detection systems cannot. Due to self shielding and long half lives, uranium can be hard to detect through conventional methods. A possible method of detection would be an active neutron imaging technique which would involve incident beams of neutrons upon the cargo container and neutron detectors surrounding the container. Using these detector readings and a constrained optimization technique, reconstructions of the material parameters inside a container can be performed to determine the contents. This is done by minimizing a cost function which is the difference between the boundary detector measurements and the boundary neutron fluxes computed from the inferred material properties inside the cargo. While many sets of material parameters have the ability to reconstruct the outer detector readings, constraints upon these must be applied. The valid constraint here will involve conservation and interaction physics of the neutrons in the container, thereby limiting the solution of material parameters to a realistic case.