Compton imager for detection of special nuclear material

A Compton imager design for the detection of Special Nuclear Material (SNM), with specific focus on shielded Highly Enriched Uranium (HEU) is presented. It is based on a large field-of-view Compton gamma-ray imager that uses 24 layers of 2 mm thick, position-sensitive (1.4mm strips) silicon detectors, designed for room-temperature operation, as a scatterer and a position-sensitive NaI scintillator array as the absorber. Each layer of silicon detectors consists of double-sided silicon strip detectors daisy chained in a 3 x 3 array with a total active area of 729 cm(2). The NaI detectors are 2.9 x 2.9 cm(2) and 7.6 cm thick and will cover the bottom and sides of the instrument. Simulations of an ASIC-based readout system show that an energy resolution of 4.5keV full-width at half-maximum (FWHM) at room temperature is attainable on each daisy-chained silicon strip assuming 35 pF of capacitance and 20 nA of leakage current. Full simulations of the current instrument design are shown and are demonstrated that it can detect 8 kg of shielded HEU at 2.5m in 1 min in a realistic gamma-ray background environment. (c) 2007 Elsevier B.V. All rights reserved.