Directly use the impulse conversion forma fast neutron for the image formation the article under the embargo detection system and the manner

摘要

A system and method for detecting contraband generates a highly collimated beam (13) of pulsed fast neutrons, having a pulse width on the order of a nanosecond, and an energy of 5 to 9 MeV. An object (14) under investigation is scanned with the collimated pulsed beam. The neutrons in the beam cause (n, η) reactions in a limited object volume or voxel, defined by the intersection of the collimated beam and the scanned object. The highly penetrating fast neutrons produce nuclear reactions with the atomic elements present within the object, causing gamma rays to be emitted. The gamma rays are detected in a gamma ray detector (20). The approximate time of flight of the neutron pulse is measured, allowing a determination to be made as to the particular voxel from which the gamma ray originated. The energy of the detected gamma rays identifies the particular elements from which the gamma rays originated. Thus, e.g., the carbon, nitrogen, oxygen, and chlorine content, which elements are commonly found in contraband, of a particular voxel can be determined directly and precisely. The voxel content information may be combined from a substantial sample of the voxels that make up the object to provide a direct indication of the elemental content of the object, and hence whether contraband is present or absent within the object.