HEAVY-ELEMENT TOMOGRAPHY USING TUNABLE GAMMA-RAY BEAMS

Gamma-ray beams of which both the bandwidth and the energy can be tune d were used to perform tomographies. Samples containing heavy elements were rotated and translated in these beams, and the absorption of the beams for each position was measured. Different analysing methods wer e compared. In contrast to common tomography which uses a continuous s pectrum, a technique relying on a monochromatic beam, and a second met hod which uses as signal the intensity ratio of two monochromatic beam s passing through the sample, are presented. When the heavy element un der study is present, with the second method the ratio becomes element sensitive if the two energies are such that one is just above and one just below the K-edge of the heavy element under study. An element-se nsitive tomography is therefore possible. Different back-projection me thods (iterative process, simple back-projection, convolution reconstr uction method) were applied on the same data, and their results were c ompared.