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3D printing technologies such as fused filament fabrication (FFF) offer great opportunities to enable the fabrication of complex geometries without access to a workshop or knowledge of machining. By adding filler materials to the raw filaments used for FFF, the material properties of the plastic can be adapted. With the addition of neutron absorbing particles, filaments can be created that enable 3D printing of neutron shielding with arbitrary geometry. Two materials for FFF are presented with different mixing ratios of hexagonal Boron nitride (h-BN) and Polylactic acid (PLA). BNPLA25 with 25 %wt h-BN and BNPLA35 with 35 %wt h-BN are compared to the commercially available Addbor N25 material. To qualify the applicability of BNPLA25 and BNPLA35 as shielding material for neutron instrumentation, such as neutron imaging, we investigated the overall neutron attenuation, the influence of non-optimized print settings, as well as characterized the incoherent neutron scattering and the microstructure using neutron imaging, and time-of-flight small-angle-neutron-scattering. Finally, the tensile strength of the material was determined in standardized tensile tests. The measured neutron attenuation shows excellent agreement with analytical calculations, thus validating both the material composition and the calculation method. Approximately 6 mm (8 mm) BNPLA35 are needed for 1 × 10 - 3 transmission of a cold (thermal) neutron beam. Lack of extrusion due to suboptimal print settings can be compensated by increased thickness, clearly visible defects can be mitigated by 11-18% increase in thickness. Incoherent scattering is shown to be strongly reduced compared to pure PLA. The tensile strength of the material is shown not to be impacted by the h-BN filler. The good agreement between the measured attenuation and calculation, combined with the adoption of safety factor enables the quick and easy development as well as the performance estimation of shielding components. BNPLA is uniquely suited for 3D printing neutron shielding because of the combination of non-abrasive h-BN particles in standard PLA, which results in a filament that can be printed with almost any off-the-shelf printer and virtually no prior experience in 3D printing. This mitigates the slightly lower attenuation observed as compared to filaments containing B 4 C , which is highly abrasive and requires extensive additive manufacturing experience., (© 2024. The Author(s).)

Grating-based phase-contrast and dark-field imaging systems create intensity modulations that are usually modeled with sinusoidal functions to extract transmission, differential-phase shift, and scatter information. Under certain system-related conditions, the modulations become non-sinusoidal and cause artifacts in conventional processing. To account for that, we introduce a piecewise-defined periodic polynomial function that resembles the physical signal formation process, modeling convolutions of binary periodic functions. Additionally, we extend the model with an iterative expectation-maximization algorithm that can account for imprecise grating positions during phase-stepping. We show that this approach can process a higher variety of simulated and experimentally acquired data, avoiding most artifacts.

High visibility (0.56) neutron-based multi-modal imaging with a Talbot-Lau interferometer at a wavelength of 1.6 Å is reported. A tomography scan of a strongly absorbing quartz geode sample was performed with both the neutron and an X-ray grating interferometer (70 kVp) for a quantitative comparison. Small scattering structures embedded in the absorbing silica matrix were well resolved in neutron dark-field CT slices with a spatial resolution of about 300 μm. Beneficial effects, such as monochromaticity and stronger penetration power of the used neutron radiation, helped to avoid the beam hardening-related artificial dark-field signal which was present in the X-ray data. Both dark-field modalities show mostly the same structures; however, some scattering features appear only in the neutron domain. Potential applications of combined X-ray and neutron multi-modal CT enabling one to probe both the nuclear and the electron density-related structural properties are discussed. strongly absorbing samples are now accessible for the dark-field modality by the use of thermal neutrons.

We performed a study of the initial and long term light yield of different scintillation screen mixtures for neutron imaging during constant neutron irradiation. We evaluated the light yield during different neutron flux levels as well as at different temperatures. As high frame rate imaging is a topic of interest in the neutron imaging community, the decay characteristics of scintillation screens are of interest as well. Hence, we also present and discuss the decay behavior of the different scintillation screen mixtures on a time scale of seconds. We have found that the decay time of ZnS:Cu/ 6 LiF excited with a high neutron flux is potentially much longer than typically stated. While most of the tested scintillation screens do not provide a significant improvement over currently used scintillation screen materials, Zn(Cd)S:Ag/ 6 LiF seems to be a good candidate for high frame rate imaging due to its high light yield, long-term stability as well as fast decay compared to the other evaluated scintillation screens.

Neutron grating interferometry (nGI) is a unique technique allowing to probe magnetic and nuclear properties of materials not accessible in standard neutron imaging. The signal-to-noise ratio of an nGI setup is strongly dependent on the achievable visibility. Hence, for analysis of weak signals or short measurement times a high visibility is desired. We developed a new Talbot-Lau interferometer using the third Talbot order with an unprecedented visibility (0.74) over a large field of view. Using the third Talbot order and the resulting decreased asymmetry allows to access a wide correlation length range. Moreover, we have used a novel technique for the production of the absorption gratings which provides nearly binary gratings even for thermal neutrons. The performance of the new interferometer is demonstrated by visualizing the local magnetic domain wall density in electrical steel sheets when influenced by residual stress induced by embossing. We demonstrate that it is possible to affect the density of the magnetic domain walls by embossing and therefore to engineer the guiding of magnetic fields in electrical steel sheets. The excellent performance of our new setup will also facilitate future studies of dynamic effects in electric steels and other systems.