Cadmium telluride detector system for identifying illicit substances by x-ray energy dispersive diffraction

We are investigating the use of cadmium telluride (CdTe) detector arrays for energy dispersive x-ray diffraction (EDXRD) for security screening applications. CdTe detectors operating at room temperature are very viable candidates to replace cryogenically cooled Ge detectors that are currently used in commercial EDXRD baggage scanning systems. Recently, we have constructed modules containing edge-on two-dimensional CdTe detector arrays. There are 22 linear detector arrays in each module. Each linear detector array has dimensions of 22 mm x 3 mm x 0.75 mm. Each linear array has 15 pixels connected to the corresponding amplification/processing channels of our ASIC electronics. The linear arrays are positioned to exactly match the output of a scatter collimator in the XDi cabin-baggage screener from Morpho Detection, GmbH. The modules have been specifically designed to minimize the cost of the materials and assembly. In contrast to area detectors, the use of linear arrays allows placement of the detectors only in the areas that are necessary to intercept x-rays but avoids areas obstructed by the scatter collimator reducing cost. We will present the system architecture and detailed performance characteristics of the detectors. The average values of energy resolution in each array in a module are between 3% and 3.1% (1.8 keV and 1.86 keV) FWHM at 60 keV with a very minimal low energy tailing in the spectra. Moreover these spectral characteristics are achieved without any software corrections for charge sharing and/or incomplete charge collection.