Evaluation of obliquely evaporated gadolinium gratings for neutron interferometry by X-ray microtomography

Gadolinium absorption gratings are critically important devices for grating-based neutron dark-field and phasecontrast imaging. The evaporation process is an excellent candidate for preparing Gd gratings large enough for imaging applications. However, there is some concern about the lower average density of obliquely evaporated Gd, which sometimes grows with many voids that are caused by shadowing effects. We have fabricated Gd gratings with 9-mu m and 4-mu m pitches as part of our design and measured the density distributions of the resulting Gd deposits by three-dimensional X-ray microtomography. The obtained tomographic image data is helpful not only for fabrication process design but also estimating device performance without performing neutron irradiation experiments.