A baggage scanning system and method employ combined angular and energy
dispersive x-ray scanning to detect the presence of a contraband
substance within an interrogation volume of a baggage item. The
interrogation volume is illuminated with penetrating, polychromatic
x-rays in a primary fan beam from a source such as a tungsten-anode x-ray
tube. An energy-dependent absorption correction is determined from
measurement of the attenuation of the fan beam at a plurality of
different energies. Radiation coherently scattered by substances in the
interrogation volume is detected by an energy-resolved x-ray detector
operated at a plurality of scattering angles to form a plurality of
scattering spectra. Each scattering spectrum is corrected for
energy-dependent absorption and the corrected spectra are combined to
produce a scattering pattern. The experimental scattering pattern is
compared with reference patterns that uniquely characterize known
contraband substances. The system and method can locate and identify a
wide variety of contraband substances in an accurate, reliable manner.
The system provides for automated screening, with the result that
vagaries of human performance are virtually eliminated. False alarms and
the need for hand inspection are reduced and detection efficacy is
increased.