Multi-energy photon-counting dual-row compound semiconductor x-ray detectors for security screening systems

We have fabricated direct conversion cadmium telluride (CdTe) and cadmium zinc telluride (CZT) semiconductor multi-energy x-ray detectors using custom application specific integrated circuits (ASICs). The detectors use a modular two side butt-able geometry and can be tiled into long dualrow one dimensional (1D) panels covering a large field of view (FoV). The CdTe and/or CZT semiconductor sensors have sub-millimeter pixel dimensions perpendicular to the scanning direction for high spatial resolution. Two rows of pixels are used for rapid scanning and to reduce the effect of individual bad pixels in scanned images. The sensors are guard ring free and three millimeters thick for high detective quantum efficiency (DQE). The mixed signal ASICs have six thresholds per pixel for up to six contiguous energy windows across a dynamic range from 20 keV to 160 keV and operate at a fast peaking time for high output count rates of up to 4 million counts per second per square millimeter (Mcps/mm ² ). Using the guard ring free sensors and geometrically integrated ASICs, multiple two-side butt-able modular detectors, each with ten centimeter FoV, have been tiled together in lengths of up to one meter. We will report the output count rate capability, dynamic range, and the spatial and energy resolution, as well as the uniformity and stability under conditions for baggage inspection in people screening lanes at airports. We will report results of imaging studies performed with a dual-view system using two such tiles of one meter of active FoV. Systems using these detectors may provide better energy separation between low and high energy x-rays as compared to dual layer or dual kVp dual energy systems, potentially leading to improved accuracy of effective atomic number (Z eff ) estimates in image voxels reconstructed from dual views. To see such an improvement, good energy resolution would need to be maintained across the expected output count rates and dynamic range.