The new neutron grating interferometer at the ANTARES beamline: design, principles and applications

Neutron grating interferometry is an advanced method in neutron imaging that allows the simultaneous recording of the transmission, the differential phase and the dark‐field image. The latter in particular has recently been the subject of much interest because of its unique contrast mechanism which marks ultra‐small‐angle neutron scattering within the sample. Hence, in neutron grating interferometry, an imaging contrast is generated by scattering of neutrons off micrometre‐sized inhomogeneities. Although the scatterer cannot be resolved, it leads to a measurable local decoherence of the beam. Here, a report is given on the design considerations, principles and applications of a new neutron grating interferometer which has recently been implemented at the ANTARES beamline at the Heinz Maier‐Leibnitz Zentrum. Its highly flexible design allows users to perform experiments such as directional and quantitative dark‐field imaging which provide spatially resolved information on the anisotropy and shape of the microstructure of the sample. A comprehensive overview of the neutron grating interferometer principle is given, followed by theoretical considerations to optimize the setup performance for different applications. Furthermore, an extensive characterization of the setup is presented and its abilities are demonstrated using selected case studies: (i) dark‐field imaging for material differentiation, (ii) directional dark‐field imaging to mark and quantify micrometre anisotropies within the sample, and (iii) quantitative dark‐field imaging, providing additional size information on the sample's microstructure by probing its autocorrelation function. In this paper the principles, design and applications of the new neutron grating interferometry (nGI) setup at the Heinz Maier‐Leibnitz Zentrum are presented. The dark‐field contrast modality of the setup allows one to obtain spatially resolved information about the microstructure of a sample. In this way, nGI closes the gap between neutron imaging and small‐angle neutron scattering.