The non-invasive inspection of baggage using coherent X-ray scattering

An inspection technique based on angular dispersive X-ray diffraction (ADXRD) has been developed to chemically specific detection of explosives for screening applications. The technique identifies explosives from benign materials using the characteristic Bragg features seen in coherently scattered X-rays. To implement this technique in a prototype screening system, a detector has been designed which, when coupled with the appropriate analysis algorithm, provides chemically specific material identification. Profile analysis has been performed using the Singular Value Decomposition (SVD) maximum likelihood technique. The detector system combines a custom designed collimator with an X-ray image intensifier tube and is capable of acquiring diffraction profiles from several independent volume elements (voxels) within the region of interest. The acquisition of spatially and energy resolved diffraction profiles for both benign and explosive materials using a separate cooled germanium detector, has allowed the data analysis algorithm to be optimised. Results from the prototype detector system show that explosives such as Semtex, RDX, and PETN have sufficient order to produce unique diffraction profiles, which may then be differentiated from benign materials.