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The detection of X-ray photons scattered through a sample by the Rayleigh and Compton processes is used to perform tomographic images. In the present paper, we describe a new experimental arrangement and the corresponding reconstruction method. The scanning method is similar to the one used for first generation tomographs. A standard reconstruction algorithm gives two intermediate images, corresponding to the Compton and Rayleigh contributions. Quantitative comparisons are made with the aim to explain the difference of sensitivity between each scattering process. On both images artifacts are present, due to photon attenuation. Computing the ratio between those two images produces a map, free from artifacts, which represents the atomic number Z . Differentiation between polyethylene and an aqueous solution containing a low concentration of iodine (0.5 g l −1 ) is easily performed. The experiments were carried out at the European Synchrotron Radiation Facility (ESRF), in Grenoble (France), on line ID15 B. As a result of the very high photon flux, short measurement times (about five seconds per point) are allowed, as well as a good spatial resolution. The voxel size is 1×1 mm 2 in the plane of the slice and 0.3 mm in the third direction. |
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