Neutron Resonance Radiography for Security Applications

James Hall
Tuesday, September 30
11:00 AM
BLDG 151, Room 1209
(Stevenson Conference Room)

Abstract:
The central problem in the use of non-intrusive techniques for the detection of explosives or contraband is to devise a reliable method for determining both the composition and shape of materials in a container. Conventional x-ray techniques based on either simple transmission measurements or high-speed computerized tomography do not actually detect explosives; rather, they "identify" objects by their apparent density and use this and shape to generate a detection signature. Unfortunately, although it is true that many explosives have, for example, densities ~1.5 g/cc, it is certainly not the case that all materials with density ~1.5 are explosives. The result, both from the point of view of physics and practical experience in airport environments is that such systems are plagued by relatively high false alarm rates.
We are currently developing a new method for detecting contraband materials based on Neutron Resonance Radiography (NRR). This technique should be capable of good spatial resolution (~ 3 mm), penetration of heavy objects, and determination of elemental composition. NRR takes advantage of element-specific resonances in total neutron at-tenuation cross sections in the 2 to 6 MeV range to enhance image contrast for elements of interest (e.g. carbon, oxygen, nitrogen, etc.). This contrast enhancement mechanism can then be used to produce elementally-resolved images of objects under inspection and thereby determine the composition of the object.
**This research is being worked on in collaboration with Richard Lanza, Massachusetts Institute of Technology