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, com prised of 88 detectors, will image contraband, such as explosives or d rugs, in a geometry similar to medical x-ray computed tomography. A po int source of gamma rays shines through an unknown object. Transmissio n projections of the areal density of detected gamma rays are reconstr ucted into a 3D image, which shows the presence of concealed contraban d inside the object. The image quality depends critically on the spati al resolution of the gamma ray detector. The new detector is a modifie d version of detectors developed by CTI for medical PET imaging with 0 .511 MeV gamma rays. A prototype detector was characterized by exposin g it to 9 MeV gamma rays from a Cf-252 + Ni source. Projection images of a simple phantom object show that the detector is capable of faithf ul imaging at 9 MeV.