Performance of gamma-ray imager using a 38 × 38 crossed-strip Ge detector

We have developed a gamma-ray imager that uses a unique hybrid germanium detector as its gamma-ray sensing element. The detector includes an eleven-millimeter thick two-millimeter pitch, 38 × 38 crossed-strip, planar, Ge detector followed by a 5-cm thick, 8-cm diameter, coaxial, Ge detector. The two-detector design significantly improves the stopping power for high energy gamma-rays over that of the planar detector alone. The images are created using the coded aperture imaging technique. A shadow mask of 6.1-mm thick Ta is used to provide imaging efficiency out to beyond 500 keV. The imager is designed for use in non-destructive analysis problems where the source configuration and overlying material is not known a priori The images are fully deconvolved to provide a spectrum at each pixel in the image. This information allows NDA techniques to be applied to each line of sight from the source, significantly improving the information obtained from a measurement. In this paper we present the details of the imager design and its performance.