Visibility simulation of realistic grating interferometers including grating geometries and energy spectra

Harti, Ralph P.; Kottler, Christian; Valsecchi, Jacopo; Jefimovs, Konstantins; Kagias, Matias; Ströbl, Markus; Grünzweig, C.

doi:10.1364/oe.25.001019

Cited by 12 publications

(15 citation statements)

References 22 publications

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“…In particular, we identified the visibility as the major contributor to the statistical uncertainty. In combination with the findings in a previous study, 17 we can conclude that improvements of the geometry of G2 will significantly decrease the uncertainty in the DFI as well as TI. Thus signal quantification is currently limited by the quality of analyser gratings which is the major contributor to reduced visibility in nGI.…”

supporting

confidence: 80%

Statistical uncertainty in the dark-field and transmission signal of grating interferometry

Harti

Ströbl

Morgano

et al. 2017

Review of Scientific Instruments

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We present a framework to estimate the fundamental statistical uncertainty of grating interferometer experiments based on a Monte-Carlo method. Using the framework, we are able to determine the uncertainty of individual measurements as well as suggesting experimental protocols that minimise the statistical uncertainty for given overall exposure times. The method presented here is valid for both X-rays and neutrons and can be generalised for any modulation measurement.

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supporting

confidence: 80%

Statistical uncertainty in the dark-field and transmission signal of grating interferometry

Harti

Ströbl

Morgano

et al. 2017

Review of Scientific Instruments

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“…distinction between dry and light water filled GDL areas is not possible with the current neutron grating interferometer setup, but there is potential for obtaining a better contrast-to-noise ratio. Noise of the DF-signal could be reduced by improving the fabrication process for the absorption grating (G2), 62 by elongating the exposure time, by using a stronger neutron source (e.g. the upcoming European Spallation Source (ESS) in Sweden), or by filtering at the cost of a reduced spatial resolution.…”

Section: Resultsmentioning

confidence: 99%

Selective Visualization of Water in Fuel Cell Gas Diffusion Layers with Neutron Dark-Field Imaging

Siegwart

Harti

Manzi-Orezzoli

et al. 2019

J. Electrochem. Soc.

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Visualizing the water distribution in porous gas diffusion layers (GDLs) of operating polymer electrolyte fuel cells (PEFCs) is indispensable to understand the impact of water management on performance. For this purpose, neutron and X-ray transmission imaging have been used for nearly two decades. Certain limitations inherent to attenuation based imaging methods can be overcome by applying neutron dark-field imaging, which has the ability to selectively visualize structures in the micrometer size range. In this study, we compare dark-field images and transmission images of GDLs filled with water through an injection channel. The high contrast of the dark-field value between a heavy water filled and a dry GDL is suitable to reveal water distribution patterns in the GDL. The water present in the 1 mm wide water injection channel of the test device does not alter the dark-field signal, as this technique is selectively sensitive to microstructures. Therefore, neutron dark-field imaging can be applied for the selective analysis of the water distribution in the GDL overlapping with channel water. In addition to the selective visualization of water distributed in a GDL, we show that neutron dark-field imaging can also be used to visualize GDL damages.

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“…An advantage for a quantitative analysis of these parameters is a high contrast of the interference pattern generated by the nGI-setup to decrease the error accrued during the measurement. Hence, the contrast produced by the nGI, denoted as visibility, may be used as a figure of merit 25 .…”

mentioning

confidence: 99%

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

Neuwirth

Backs

Gustschin

et al. 2020

Sci Rep

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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. Neutron radiography is a method allowing for non-destructive analysis of the inner structure of an object 1. Because the neutron cross-sections show no systematic dependence on the atomic number, both light and heavy elements can be visualized. Moreover, the contrast between different materials can be varied by using isotopes. Therefore, neutron imaging has been established to be a very efficient technique in materials science, research in cultural heritage, archaeology, and engineering, where imaging with X-rays fails to produce sufficient contrast. Neutron imaging is, however, limited by the coarse spatial resolution imposed by the limitations in neutron flux and the spatial resolution of the neutron detectors. Currently, the achieved spatial resolution is in the low single μm range 2-7. Paths towards resolving structures with higher resolution (e.g. water transport in fuel cells) are, for example, improving the detector resolution 3-6 or in some cases using neutron grating interferometry (nGI) 8,9 as a spatially resolved ultra-small-angle scattering technique. nGI simultaneously gathers spatially resolved information about the transmission-(TI), the differential phase contrast-(DPCI) and the scattering/dark-field (DFI) of a sample. Most notably, the contrast provided by the DFI 10,11 is generated by ultra-small-angle neutron scattering (USANS) off structures on a length scale similar to the correlation length of the interferometer setup, which is typically in the range 0.1 μm to 10 μm. Such structures are caused by variations of the nuclear or magnetic

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Visibility simulation of realistic grating interferometers including grating geometries and energy spectra

Cited by 12 publications

References 22 publications

Statistical uncertainty in the dark-field and transmission signal of grating interferometry

Statistical uncertainty in the dark-field and transmission signal of grating interferometry

Selective Visualization of Water in Fuel Cell Gas Diffusion Layers with Neutron Dark-Field Imaging

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

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