Search

Liquefied noble gas (LNG) detectors have already been successfully employed in areas of fundamental particle physics research due to features such as their high energy resolution, fast response times, excellent discrimination between neutron and gamma-ray interactions, and relatively low cost. Such detectors are also attractive for nonintrusive inspection for the presence of special nuclear material (SNM) in large-scale objects such as cargo containers and trucks. An effective method of interrogation involves pulsing the object being interrogated with neutrons, which induces fission in the SNM. The fission reaction promptly releases gamma rays and neutrons. This reaction can be distinguished from background through the coincidence measurement of these particles striking multiple detectors. Rapiscan Laboratories, Yale University Physics Department, and Adelphi Technology have constructed two 18-L liquid argon prototype detectors to investigate the suitability of LNG detectors in performing this form of interrogation. The pulse shape, energy resolution, time resolution, detector efficiency, and the effects of doping with xenon were measured. [ABSTRACT FROM PUBLISHER]

A study is presented on the detection of illicit special nuclear materials (SNM) in cargo containers using a conceptual neutron-based inspection system with xenon-doped liquefied argon (LAr(Xe)) scintillation detectors for coincidence gamma-ray detection. For robustness, the system is envisioned to exploit all fission signatures, namely both prompt and delayed neutron and gamma emissions from fission reactions induced in SNM. However, this paper focuses exclusively on the analysis of the prompt gamma ray emissions. The inspection system probes a container using neutrons produced either by (d, D) or (d, T) in pulsed form or from an associated particle neutron generator to exploit the associated particle imaging (API) technique, thereby achieving background reduction and imaging. Simulated signal and background estimates were obtained in MCNPX (2.7) for a 2 kg sphere of enriched uranium positioned at the center of a 1\ m\times 1\ m\times 1\ m container, which is filled uniformly with wood or iron cargos at 0.1 g/cc or 0.4 g/cc. Detection time estimates are reported assuming probabilities of detection of 95% and false alarm of 0.5%. [ABSTRACT FROM PUBLISHER]