| ABSTRACT: | PHASE TOMOGRAPHY IN NEUTRON INTERFEROMETRY
M. Zawisky1, U. Bonse2, F. Dubus1, R. Loidl1, Z. Hradil3, J. Rehacek3
1 Atominstitute of the Austrian Universities, Vienna, Austria; 2 University of Dortmund, Dortmund,
Germany; 3 Palacky University, Olomouc, Czech Republic
Perfect crystal neutron interferometers enable the simultaneous investigation of different interactions like
absorption, small angle scattering, and forward scattering. The coherent forward scattering of neutrons in
materials or magnetic fields generates phase shifts, which are not influenced by the beam attenuation in the
sample. In perfect crystal neutron interferometry small phase shifts of thermal neutrons can be detected with
high sensitivity. The tomographic reconstruction of phase projections is similar to that of transmission
tomography, but due to the larger fluctuations of count numbers and phases an optimized maximum
likelihood algorithm has to be involved. In the first part of our presentation the principles and experimental
requirements for interferometric tomography are discussed. Then we introduce a maximum likelihood
routine for the reconstruction of strong fluctuating quantities. Finally we show first experimental results, the
analysis of isotope mixtures and the investigation of a metal composite, both materials are nearly transparent
to thermal neutron beams. The neutron phase tomography proves its strength in extreme applications where
other methods fail, e.g., the complete 3D analysis of non- or weak-absorbing substances and isotope
distributions, the sensitive detection of liquids, residues and corrosion in metals, and the investigation of
magnetic domains in bulk materials.
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