X-ray diffraction imaging system for the detection of illicit substances using pixelated CZT-detectors

Abstract

The use of energy-dispersive X-ray diffraction (XRD) in security screening applications allows for highest detection and lowest false-alarm rates. So far, only Germanium-detectors have been used in commercially available XRD baggage-scanning systems, limiting the available detection area due to technical and commercial reasons, and as a consequence, the achievable throughput. Morpho Detection has built an innovative X-ray diffraction imaging (XDi) system equipped with 17 pixelated Cadmium-Zinc-Telluride (CZT) detector modules for increased detection-area to alleviate this limitation. A multi-focus X-ray source (MFXS) allows for high X-ray flux and makes any other mechanical movement, except for the bags, obsolete. In conjunction with a dedicated collimation system the detectors measure the scatter from the bag spatially and energetically resolved, allowing for a voxelized reconstruction of the bag's scatter-signature. The detector-array is required to deliver spectra of high quality, calling for very good energy-resolution and efficiencies, which is why signal-corrections are performed on-board. Each module is a completely independent unit to ensure service friendliness, receiving just one voltage, a trigger and Ethernet for control and data-transfer. We will explain the functional principle of the XDi -system, present the performance of the detectors with respect to stability and show spectra of different materials and reconstructed 3-D feature maps.