A dual X-ray backscatter system for detecting explosives: Image and discrimination of a suspicious content

Most of luggage inspection systems, searching for presence of an explosive threat, are based either on X-ray transmission technologies, such as radiography and computed tomography, or X-ray diffraction analysis (small angle coherent scattering). These techniques have limitations, especially in case of large or dense objects or if they are placed close to a wall not allowing access to the rear side for radiography (for instance an abandoned luggage). Portable systems using backscattered X-rays can be alternative solutions to analyze a suspicious object from one side, without any contact, especially in Homeland Security applications. Such systems are not currently available. X-ray backscatter imaging, unlike X-ray radiography, reveals low Z materials, as explosives, hidden inside a luggage or behind a screen. Moreover, a specific analysis of backscattered spectra can give information about the suspicious material localized in the backscatter image, in order to discriminate whether it is explosive or inert. In this article, we present these two processes, dedicated to imaging and discrimination, developed as laboratory prototypes. They are based on the use of a manufactured portable X-ray tube. Experimental results are presented, demonstrating the performance and potentialities of such a dual system.