Cold and Thermal Neutron Single Grating Dark-Field Imaging Extended to an Inverse Pattern Regime

Neutron dark-field imaging is a powerful tool for the spatially resolved characterization of microstructural features of materials and components. Recently, a novel achromatic technique based on a single absorption grating for the concurrent measurement of attenuation, dark-field and differential phase contrast was introduced. However, the range of measurable length scales of the technique in quantitative dark-field measurements appeared limited to some 10–100 nanometers, due to the relatively high spatial resolution requirement to detect the projected beam modulation. Here, we show how using grating–detector distances beyond the resolution limit for a given collimation produces a sequence of inverse and regular projection patterns and, thus, leads to a significant extension of the range of accessible length scales probed by dark-field imaging. In addition, we show that this concept can also be applied to 2D grating structures, which will enable concurrent three-fold directional dark-field measurements at a wide range of length scales. The approach is demonstrated with measurements on an electrical steel sheet sample, which confirm the validity of combining the results from the regular and inverse grating patterns.