A position sensitive detector for 1-10 MeV gamma rays

A position sensitive detector for 9 MeV gamma rays has been developed as part of a contraband detection system for airports. The system, comprised of 88 detectors, will image contraband, such as explosives or drugs, in a geometry similar to medical X-ray computed tomography. A point source of gamma rays shines through an unknown object. Transmission projections of the areal density of detected gamma rays are reconstructed into a 3D image, which shows the presence of concealed contraband inside the object. The image quality depends critically on the spatial resolution of the gamma ray detector. The new detector is a modified version of detectors developed by CTI for medical PET imaging with 0.511 MeV gamma rays. A prototype detector was characterized by exposing it to 9 MeV gamma rays from a /sup 252/Cf+Ni source. Projection images of a simple phantom object show that the detector is capable of faithful imaging at 9 MeV.