Observation of subgrain boundaries and dislocations by neutron diffraction topography

We have improved the resolution of neutron diffraction topography by working with a low-divergence primary beam from a neutron guide tube and using an almost perfect monochromator. As a result, we have obtained neutron topographs revealing, although with a resolution still very inferior to that of x-ray topography, subgrain boundaries and inclusions in a Fe-2.5 wt% Si single crystal, as well as some individual dislocations in a germanium single crystal. Their contrast is compared with that of x-ray topographs of the same specimens and discussed.