Using a superconducting cyclotron to detect special nuclear material through multiple monoenergetic gamma radiography and o-axis photon scattering/

Abstract

This thesis reports on using a superconducting compact proton cyclotron to conduct multiple monoenergetic gamma radiography (MMGR) and measure o-axis photon scattering to nd special nuclear material (SNM). The cyclotron is a small enough accelerator to be a viable option for scanning commercial cargo containers at maritime ports, airports, rail crossings, and other places of interest. This research presents a technique for reconstructing the eective atomic number (Z) and areal density ([rho][subscript A]) of cargo mock-ups using MMGR with the cyclotron, analyzes the sensitivity of the reconstruction technique, and applies the technique to experimental data. However, single-axis radiography is prone to hoaxing by smugglers. It is relatively trivial to make high-Z material such as SNM look like an innocuous, lower-Z material, such as iron, by surrounding the high-Z material with low-Z material like polyethylene or aluminum. To secure MMGR from this risk of hoaxing, this research presents the use of large angle photon scatter ([theta] = 125°) in cargo to gain additional information on its atomic number. The MMGR technique is found to be able to resolve materials of Z < 70 and uranium (Z = 92); however, the technique has difficulty resolving lead from uranium. Off-axis photon scattering is found to contain Z-specfic information in Monte Carlo simulations, but experimental results are inconclusive.