The design of direct tomographic energy-dispersive x-ray diffraction imaging (XDI) systems

Abstract

The most complex components of an energy dispersive x-ray diffraction imaging (XDI) system are in general the radiation source and the spectroscopic detector array. Hence it is important to determine the geometrical factors affecting the size and shape of these components in arbitrary XDI configurations. These factors strongly influence system design parameters such as complexity, size and cost. Following an introduction to the physical principles of x-ray diffraction imaging (XDI) a generic 2-D cross section of an arbitrary tomographic XDI system is proposed. It is shown that a 3-D XDI arrangement can always be synthesised from identical 2-D generic sections when these are replicated along lines running through the vertex of an axially symmetric conic surface. The geometry of the cone and thus of the corresponding XDI system is determined by three arbitrary, independent parameters. There is thus an infinite number of possible alternative XDI configurations. The design of several variant XDI systems of potential interest for checked baggage inspection is discussed with reference to component size and complexity. These alternative configurations are described in this paper and their relative merits assessed. The procedure described here is useful both for optimising the performance of an XDI system of given complexity and for adapting the geometry of an XDI system to components of given specifications.