Statistical Image Reconstruction for High-Throughput Thermal Neutron Computed Tomography

Neutron Computed Tomography (CT) is an increasingly utilised non-destructive analysis tool in material science, palaeontology, and cultural heritage. With the development of new neutron imaging facilities (such as DINGO, ANSTO, Australia) new opportunities arise to maximise their performance through the implementation of statistically driven image reconstruction methods which have yet to see wide scale application in neutron transmission tomography. This work outlines the implementation of a convex algorithm statistical image reconstruction framework applicable to the geometry of most neutron tomography instruments with the aim of obtaining similar imaging quality to conventional ramp filtered back-projection via the inverse Radon transform, but using a lower number of measured projections to increase object throughput. Through comparison of the output of these two frameworks using a tomographic scan of a known 3 material cylindrical phantom obtain with the DINGO neutron radiography instrument (ANSTO, Australia), this work illustrates the advantages of statistical image reconstruction techniques over conventional filter back-projection. It was found that the statistical image reconstruction framework was capable of obtaining image estimates of similar quality with respect to filtered back-projection using only 12.5% the number of projections, potentially increasing object throughput at neutron imaging facilities such as DINGO eight-fold

Structural Characterization of Iron Meteorites through Neutron Tomography

In this communication, we demonstrate the use of neutron tomography for the structural characterization of iron meteorites. These materials prevalently consist of metallic iron with variable nickel content. Their study and classification is traditionally based on chemical and structural analysis. The latter requires cutting, polishing and chemical etching of large slabs of the sample in order to determine the average width of the largest kamacite lamellae. Although this approach is useful to infer the genetical history of these meteorites, it is not applicable to small or precious samples. On the base of different attenuation coefficient of cold neutrons for nickel and iron, neutron tomography allows the reconstruction of the Ni-rich (taenite) and Ni-poor (kamacite) metallic phases. Therefore, the measure of the average width of the largest kamacite lamellae could be determined in a non-destructive way. Furthermore, the size, shape, and spatial correlation between kamacite and taenite crystals were obtained more efficiently and accurately than via metallographic investigation

Microstructure and texture analysis of δ-hydride precipitation in Zircaloy-4 materials by electron microscopy and neutron diffraction

This work presents a detailed microstructure and texture study of various hydrided Zircaloy-4 materials by neutron diffraction and microscopy. The results show that the precipitated δ-ZrH1.66 generally follows the δ (111) //α (0001) and δ[]//α[] orientation relationship with the α-Zr matrix. The δ-hydride displays a weak texture that is determined by the texture of the α-Zr matrix, and this dependence essentially originates from the observed orientation correlation between α-Zr and δ-hydride. Neutron diffraction line profile analysis and high-resolution transmission electron microscopy observations reveal a significant number of dislocations present in the δ-hydride, with an estimated average density one order of magnitude higher than that in the α-Zr matrix, which contributes to the accommodation of the substantial misfit strains associated with hydride precipitation in the α-Zr matrix. The present observations provide an insight into the behaviour of δ-hydride precipitation in zirconium alloys and may help with understanding the induced embrittling effect of hydrides.Fil: Wang, Zhiyang. University of Wollongong; Australia. Australian Nuclear Science and Technology Organisation; AustraliaFil: Garbe, Ulf. Australian Nuclear Science and Technology Organisation; AustraliaFil: Li, Huijun. University of Wollongong; AustraliaFil: Wang, Yanbo. University of Sydney; AustraliaFil: Studer, Andrew J.. Australian Nuclear Science and Technology Organisation; AustraliaFil: Sun, Guangai. Institute of Nuclear Physics and Chemistry, CAEP; ChinaFil: Harrison, Robert P.. Australian Nuclear Science and Technology Organisation, Institute of Materials Engineering; AustraliaFil: Liao, Xiaozhou. University of Sydney; AustraliaFil: Vicente Alvarez, Miguel Angel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santisteban, Javier Roberto. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kong, Charlie. University of New South Wales; Australi

New material of the ‘microsaur’ Llistrofus from the cave deposits of Richards Spur, Oklahoma and the paleoecology of the Hapsidopareiidae

The Hapsidopareiidae is a group of “microsaurs” characterized by a substantial reduction of several elements in the cheek region that results in a prominent, enlarged temporal emargination. The clade comprises two markedly similar taxa from the early Permian of Oklahoma, Hapsidopareion lepton and Llistrofus pricei, which have been suggested to be synonymous by past workers. Llistrofus was previously known solely from the holotype found near Richards Spur, which consists of a dorsoventrally compressed skull in which the internal structures are difficult to characterize. Here, we present data from two new specimens of Llistrofus. This includes data collected through the use of neutron tomography, which revealed important new details of the palate and the neurocranium. Important questions within “Microsauria” related to the evolutionary transformations that likely occurred as part of the acquisition of the highly modified recumbirostran morphology for a fossorial ecology justify detailed reexamination of less well-studied taxa, such as Llistrofus. Although this study eliminates all but one of the previous features that differentiated Llistrofus and Hapsidopareion, the new data and redescription identify new features that justify the maintained separation of the two hapsidopareiids. Llistrofus possesses some of the adaptations for a fossorial lifestyle that have been identified in recumbirostrans but with a lesser degree of modification (e.g., reduced neurocranial ossification and mandibular modification). Incorporating the new data for Llistrofus into an existing phylogenetic matrix maintains the Hapsidopareiidae’s (Llistrofus + Hapsidopareion) position as the sister group to Recumbirostra. Given its phylogenetic position, we contextualize Llistrofus within the broader “microsaur” framework. Specifically, we propose that Llistrofus may have been fossorial but was probably incapable of active burrowing in the fashion of recumbirostrans, which had more consolidated and reinforced skulls. Llistrofus may represent an earlier stage in the step-wise acquisition of the derived recumbirostran morphology and paleoecology, furthering our understanding of the evolutionary history of “microsaurs.

Neutron ghost imaging

Ghost imaging is demonstrated using a polyenergetic reactor source of thermal neutrons. This enables position resolution to be incorporated into a variety of neutron instruments that are not position resolving. Such a proof of concept enables several further applications. For example, in an imaging context, neutron ghost imaging can be beneficial for dose reduction and resolution enhancement. We explore the principle of resolution enhancement by employing a variant of the method in which each pixel of a position-sensitive detector is regarded as an independent bucket detector; a neutron ghost image is then computed for each pixel. We demonstrate the principle that this parallel form of neutron ghost imaging can significantly increase the spatial resolution of a pixelated detector such as a CCD or CMOS camera. Further applications and extensions of our neutron ghost-imaging protocol are discussed. These include neutron ghost tomography, neutron ghost microscopy, dark-field neutron ghost imaging, and isotope-resolved color neutron ghost imaging via prompt-gamma-ray bucket detection.A.M.K. and G.R.M. acknowledge the financial support of the Australian Research Council and FEI-Thermo Fisher Scientific through Linkage Project No. LP150101040, and the use of supercomputer time provided by Australia’s National Computational Infrastructure (NCI)

Texture Development in Two-Phases Stream

Strömende Gemische aus flüssigen und festen Phasen treten bei unterschiedlichen Prozessen wie z. B. beim Blutkreislauf des Menschen, bei der Grünformung von Keramiken und beim fließen von teilkristallisierten Schmelzen auf. Ein wesentlicher Vorgang innerhalb dieser Gemische ist die Orientierung der kristallinen Teilchen in der strömenden Flüssigkeit. Dies beeinflusst sowohl die physikalischen Eigenschaften der Gemische als auch die daraus resultierenden Eigenschaften der Endprodukte wie im Falle der Grünformung von Keramiken. Die Bestimmung der Orientierung der kristallinen Partikel erfolgte mittels Diffraktion. Für diese Methode ist die Hochenergetische Synchrotronstrahlung aufgrund der hohen Eindringtiefe im zu untersuchenden Material sehr gut geeignet. Um die Messungen direkt am strömenden Material durchzuführen, wurden zwei Strömungsküvetten konstruiert. Bisherige Untersuchungen fanden entweder nach vollendeter Strömung (eingefrorener Zustand) statt, oder es wurden nur kleine Bereiche des Orientierungsraums (in eine Richtung) erfasst. Es wurde eine Rotationsküvette, bei der eine Scherströmung durch eine rotierende Scheibe in einem Zylinder erzeugt wird und eine Durchflussküvette zum erzeugen einer Rohrströmung entwickelt.In dieser Arbeit wurden erstmals die zur Orientierungsbestimmung und 3 dimensionalen Texturanalyse benötigten Polfiguren an der HASYLAB Beamline BW5 aufgenommen. Die Messungen fanden an plättchenförmigen Muskovitteilchen als Modellsubstanz und Aluminiumoxidteilchen unterschiedlicher Form als materialwissenschaftlich relevanter Substanz statt. Mit diesen Ergebnissen ließen sich theoretische Berechnungen über die Orientierung einzelner Teilchen in einer Flüssigkeit auf die Gültigkeit in hochkonzentrierten Zwei-Phasen-Strömungen überprüfen. Die von Jeffery vorhergesagte Ausrichtung der Plättchenebene parallel zur Strömungsrichtung wurde von allen Messungen bestätigt. Für Muskovit wurde jedoch eine weitere Vorzugsorientierung gefunden, welche zeigt, dass die freie Rotation um die Plättchennormale nur unvollständig ist. Die Untersuchungen an den Aluminiumoxidpartikeln haben gezeigt, dass die Ausrichtung der Plättchenebene parallel zur Strömungsrichtung mit steigender Feststoffkonzentration immer schwächer ausgeprägt ist und somit stärker von Verhalten eines isolierten Teilchens in der Strömung abweicht. Außerdem wurde auch der Einfluss der Plättchenform auf die Orientierungsdichte untersucht, welcher mit stark ausgeprägter Plättchenform entsprechend den Erwartungen zu schärferen Texturen führt. Diese Vergleiche von Messungen an Gemischen unterschiedlicher Feststoffkonzentration lassen sich nur mit Hilfe der Polfigurmessung mit anschließender 3-dimensionalen Texturanalyse durchführen. Nur so erhält man normierte Daten für die Orientierungsverteilung und kann Orientierungsdichten aus unterschiedlichen Messungen miteinander vergleichen. Die in dieser Arbeit entwickelte Methode lässt sich auch auf andere Systeme ausweiten und liefert ein besseres Verständnis vom Verhalten von festen Partikeln in einer strömenden Flüssigkeit

Statistical image reconstruction for high-throughput thermal Neutron Computed Tomography

Neutron Computed Tomography (CT) is an increasingly utilised non-destructive analysis tool in material science, palaeontology, and cultural heritage. With the development of new neutron imaging facilities (such as DINGO, ANSTO, Australia) new opportunities arise to maximise their performance through the implementation of statistically driven image reconstruction methods which have yet to see wide scale application in neutron transmission tomography. This work outlines the implementation of a convex algorithm statistical image reconstruction framework applicable to the geometry of most neutron tomography instruments with the aim of obtaining similar imaging quality to conventional ramp filtered back-projection via the inverse Radon transform, but using a lower number of measured projections to increase object throughput. Through comparison of the output of these two frameworks using a tomographic scan of a known 3 material cylindrical phantom obtain with the DINGO neutron radiography instrument (ANSTO, Australia), this work illustrates the advantages of statistical image reconstruction techniques over conventional filter back-projection. It was found that the statistical image reconstruction framework was capable of obtaining image estimates of similar quality with respect to filtered back-projection using only 12.5% the number of projections, potentially increasing object throughput at neutron imaging facilities such as DINGO eight-fold