Dynamic volume magnetic domain wall imaging in grain oriented electrical steel at power frequencies with accumulative high-frame rate neutron dark-field imaging

Harti, Ralph P.; Ströbl, Markus; Schäfer, Rudolf; Kardjilov, Nikolay; Tremsin, Anton S.; Grünzweig, C.

doi:10.1038/s41598-018-33835-8

Cited by 21 publications

(18 citation statements)

References 23 publications

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“…Furthermore, the better signal-to-noise ratio of the new nGI allows conducting experiments with shorter exposure times. Hence, experiments analyzing the response of the magnetic domains in an alternating magnetic field, which is used in electric machines, can be performed stroboscopically 45 . Also samples which could not be investigated so far can now be probed.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…Already that has enabled a number of distinguished studies visualizing e.g. structural flaws in engineering materials 5–9 and in particular magnetic domain structures in the volume of bulk materials 10–17 , where they are not assessable by any other means. However, based on the small-angle scattering theory a description of dark-field contrast became available 18 , which in analogy to spin-echo small-angle scattering, enables quantitative assessment of the scattering structures 19–24 .…”

Section: Introductionmentioning

confidence: 99%

Symmetric Talbot-Lau neutron grating interferometry and incoherent scattering correction for quantitative dark-field imaging

Kim

Valsecchi

Kim

et al. 2019

Sci Rep

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We introduce the application of a symmetric Talbot-Lau neutron grating interferometer which provides a significantly extended autocorrelation length range essential for quantitative dark-field contrast imaging. The highly efficient set-up overcomes the limitation of the conventional Talbot-Lau technique to a severely limited micrometer range as well as the limitation of the other advanced dark-field imaging techniques in the nanometer regime. The novel set-up enables efficient and continuous dark-field contrast imaging providing quantitative small-angle neutron scattering information for structures in a regime from some tens of nanometers to several tens of micrometers. The quantitative analysis enabled in and by such an extended range is demonstrated through application to reference sample systems of the diluted polystyrene particle in aqueous solutions. Here we additionally demonstrate and successfully discuss the correction for incoherent scattering. This correction results to be necessary to achieve meaningful quantitative structural results. Furthermore, we present the measurements, data modelling and analysis of the two distinct kinds of cohesive powders enabled by the novel approach, revealing the significant structural differences of their fractal nature.

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“…The neutron DFI signal was then adopted for tomographic investigations providing non-magnetic, spatially resolved information about the distribution of micrometer and sub-micrometer-sized structural formations 28 . Another main field of research by means of DFI is the visualization of magnetic domain structures in bulk ferromagnetic grain-oriented electrical steels 10,29–35 . An emerging topic of interest for DFI is the investigation of local magnetic phenomena in superconductors, such as the domain distribution in the intermediate state of Lead 36 and the morphology of lattice domains in type-II superconductor 37,38 .…”

Section: Introductionmentioning

confidence: 99%

Visualization and quantification of inhomogeneous and anisotropic magnetic fields by polarized neutron grating interferometry

et al. 2019

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The intrinsic magnetic moment of a neutron, combined with its charge neutrality, is a unique property which allows the investigation of magnetic phenomena in matter. Here we present how the utilization of a cold polarized neutron beam in neutron grating interferometry enables the visualization and characterization of magnetic properties on a microscopic scale in macroscopic samples. The measured signal originates from the phase shift induced by the magnetic potential. Our method enables the detection of previously inaccessible magnetic field gradients, in the order of T cm −1 , extending the probed range by an order of magnitude. We visualize and quantify the phase shift induced by a well-defined square shaped uniaxial magnetic field and validate our experimental findings with theoretical calculations based on Hall probe measurements of the magnetic field distribution. This allows us to further extend our studies to investigations of inhomogeneous and anisotropic magnetic field distribution.

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Dynamic volume magnetic domain wall imaging in grain oriented electrical steel at power frequencies with accumulative high-frame rate neutron dark-field imaging

Cited by 21 publications

References 23 publications

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

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

Symmetric Talbot-Lau neutron grating interferometry and incoherent scattering correction for quantitative dark-field imaging

Visualization and quantification of inhomogeneous and anisotropic magnetic fields by polarized neutron grating interferometry

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