Neutron Dark-Field Tomography

Abstract

We report how a grating interferometer yields neutron dark-field scatter images for tomographic investigations. The image contrast is based on ultrasmall-angle scattering. It provides otherwise inaccessible spatially resolved information about the distribution of micrometer and submicrometer sized structural formations. Three complementary sets of tomographic data corresponding to attenuation, differential phase, and small-angle scattering can be obtained from one measurement. The method is compatible with conventional imaging and provides significantly higher efficiency than existing techniques.

TOF-SEMSANS—Time-of-flight spin-echo modulated small-angle neutron scattering

“…13 Furthermore, the lack of substantial collimation requirements enables to investigate large area samples with spatial resolution, i.e., in a dark-field imaging mode. 14,15 …”

Three-dimensional imaging of magnetic domains

“…For a successful 3D reconstruction of the domain structure, a dedicated algorithm had to be developed. Although image contrast is achieved through dark-field evaluation, it originates from refraction and thus involves a significant angular dependence (comparable to (synchrotron) X-ray phase contrast tomography with edge enhancement) 13,15,24,25 . However, we applied our own iterative reconstruction algorithm (DIRECTT), which is especially suitable for incomplete data sets such as missing projection angles and insufficient transmission intensities 26 .…”

“…S1b), the intensity of which is increased by refraction at magnetic domain walls present in any sample placed between G S and G A . By stepwise rotation (360°) of the sample around the vertical axis, several projection images are taken 13 that contain information about all magnetic domain walls in the sample (limited only by the spatial resolution).…”

“…An exposure time of 100 s per radiographic image was chosen. The data set was corrected by additional background and flat field measurements, and the dark-field signal was evaluated by a sinusoidal fitting routine 13,10 .…”

“…Well-aligned domain walls in a thin ferromagnetic plate have also been investigated using the superior method of phase grating interferometry for (2D) neutron dark-field imaging [10][11][12][13] . In both cases, the image contrast is based on the refraction of neutrons at domain walls 14 .…”