The feasibility of searching for contraband materials using a gamma-ray ´radar´ system

A technique for searching for contraband materials that may be hidden behind a barrier is described. This imaging technique is based on the detection of one of the two annihilation photons produced by a positron-emitter that has scattered in the target, in coincidence with the detection of the second photon in a position-sensitive scintillation counter. The results of a feasibility study will be presented in which a 1mCi source was used to illuminate a 1times1 m² area to provide a two dimensional image of the line-of-sight density within this object. The spatial-resolution achievable is -1times1 cm. Details of the detector design envisaged for this application will be described and the images generated through Monte Carlo simulations presented.