Tomography using monochromatic thermal neutrons with attenuation and phase contrast

Attenuation-contrast tomography with monochromatic thermal neutrons was developed and operated at guide station S 18 of he institute Laue-Langevin in Grenoble. From the S 18 spectrum the neutron wavelength lambda = 0. 18 nm was selected by employing a fore crystal with the silicon 220 reflection at a Bragg angle circle minus = 30degrees. Projections were registered by a position sensitive detector (PSD) consisting of a neutron-to-visible-light converter coupled to a CCD detector. Neutron tomography and its comparison with X-ray tomography is studied. This is of special interest since the cross section for neutron attenuation (sigma(atom)) and the cross section for neutron phase shift (b(c)) are isotope specific and, in addition, by no means mostly monotonous functions of atomic number Z as are attenuation coefficient (mu(x)) and atomic scattering amplitude (f) in the case of X-rays. Results obtained with n-attenuation tomography will be presented. Possibilities and the set-up of an instrument for neutron phase-contrast tomography based on single-crystal neutron interferometry will be described.