Low angle X-ray scatter for explosives detection: A geometry optimization

A geometry has been established for a low angle X-ray scatter (LAXS) system for the detection of sheet explosive in passenger baggage. The energy dispersive diffraction profiles of two typical explosives, PE4 and Semtex, have been investigated under a wide range of geometric conditions. A scatter angle of 5° and a slit collimation arrangement with an angular resolution of 20% has been found to satisfy the required criteria of well-defined, high intensity diffraction profiles at the sufficiently high energies necessary to penetrate baggage items. An investigation of typical benign suitcase contents under the optimal geometry show in general broad low-order diffraction profiles in contrast to the highly characteristic diffraction from the explosives. Real time measurement of explosives show that characteristic diffraction profiles can be measured in times as short as 0.1 s although a large statistical uncertainty results.