الفهرس | Only 14 pages are availabe for public view |
Abstract The potential of computerized tomography by neutrons and gamma rays as a main technique for non-destructive assay of materials and components of prime importance in nuclear and general industries are given and discussed. Both Fast Fourier Transform (FFT) and Algebraic Reconstruction Technique (ART) techniques are introduced and discussed. Shepp and Logan human head phantom is used for theoretical testing and studying the effective measuring parameters and image reconstruction parameters for both techniques. An experimental verification of successful of both techniques for image reconstruction is performed by using transmitted gamma rays projected data through standard test sample. Comparison between the two techniques has been carried out for the examined object. The artifacts, caused in the reconstructed image due to the spectrum shift to higher energies, spectrum hardening and to lower energies, spectrum softening of the transmitted fast neutrons and gamma rays have been corrected by the two-channel spectroscopy technique. In this technique, the two-channel spectroscopy device was coupled with the neutron/gamma discriminator unit and the correction treatments were performed on-line during the measurement. Some neutron and gamma CT-images, which have been be reconstructed from the projected data measured with and without spectral correction have been given to show the effect of this correction method. |