Security

This system has potential applications in the security, decommissioning and medical fields.  The system is designed to utilise a stack of thin room temperature semiconductor detectors. These comprise of 2 mm thick silicon (Si) detectors and cadmium zinc telluride (CZT) detectors with thicknesses of 2 and 5 mm. Each of these detectors is segmented into 100 pixels and is read out through custom designed Application Specific Integrated Circuits (ASICs). The imaging capability utilises the Compton Camera principle, requiring a gamma ray to undergo a Compton scattering interaction and then be photo-electrically absorbed. Previous work with a prototype system (PorGamRayS) has demonstrated imaging capability with a resolution of < 20 mm.‌

Using a pulsed x-ray source the time of flight of the backscattered x-rays will be measured with an array of scintillation detectors in order to obtain data that can be used to create a three dimensional image. Preliminary experiments at the VELA facility at Daresbury using a single detector have shown a relationship between the time of flight and the position and composition of an object. As the time of flight is a few nanoseconds it is necessary to develop a fast digital data acquisition system for the detector array.

The array of up to eight scintillation detectors and the data acquisition system will be used at the VELA facility at Daresbury to collect data that will be analysed to show the potential for producing three dimensional images. The system will then be used at a Rapiscan's facility in Stoke where the pulsed x-ray beam is more like those that could be widely deployed.