Quantitative sorting using dual energy X-ray transmission imaging

Dual energy techniques are well-known methods in X-ray transmission imaging. However they are not commonly used in a quantitative manner in sorting applications. We introduce a method called Basis Material Decomposition (BMD) that allows the determination of the fraction of mass of different, a priori known materials using two X-ray spectra and/or spectral detector efficiencies for dual energy X-ray imaging. The method exploits the dependency of the X-ray attenuation on density and atomic number of the object and the energy of the X-rays. One example is the quantitative sorting of pollutants from valuable material, e.g. halogens as bromine from plastics to enhance their recovery rate significantly. A possible application in mining is the detection and sorting of diamonds from the host ore kimberlite, allowing diamonds to be detected even if they are covered in mud or dust or completely enclosed in the ore. We present measurements from a lab setup and discuss how this approach can provide benefits in an industrial environment in the near future.