Neutron CT Research Articles

Sparse-view neutron CT 3D image reconstruction algorithm based on split Bregman method

Sparse-view neutron CT 3D image reconstruction algorithm based on split Bregman method

Split Bregman quantum noise removal algorithm for 3D reconstruction of neutron computed tomography image

The low intensity of the neutron source for neutron computed tomography (CT) results in a long acquisition time for a single projection, which causes the neutron projection data to contain a large amount of quantum noise. Quantum noise will degrade the quality of neutron CT reconstruction images. Therefore, an efficient quantum noise removal algorithm must be used in CT reconstruction. In this paper, an efficient quantum noise removal algorithm for neutron CT 3D image reconstruction is proposed by analysing classical image processing algorithms and quantum image processing algorithms, which employs the maximum likelihood expectation maximization to reconstruct the image and split Bregman algorithm to solve for the total variation (MLEM-SBTV). Experimental results show that MLEM-SBTV performs well in removing quantum noise and reconstructing the detailed structure of images.

Understanding water dynamics in operating fuel cells by operando neutron tomography: investigation of different flow field designs

Water management plays a key role in ensuring optimum polymer electrolyte fuel cell (PEFC) performance, and flow field design can influence the ability of a cell to balance maintaining hydration, whilst avoiding flooding and cell failure. This work deepens the understanding of water evolution in different PEFC flow channel designs, namely single serpentine (SS), double serpentine (DS) and parallel, using our novel high-speed neutron computed tomography method. We developed our previously-reported method by introducing continuous cell rotation, enabling 18 s per tomogram during 1 h holds at 300, 400 and 500 mA cm−2. The volume of water evolved in the cathode, membrane electrode assembly and anode was quantified, and key mechanisms for water droplet formation in the different flow channel designs were elucidated. The parallel flow field design had the poorest water management, with 47% of the cathode flow channel becoming filled after 1 h at 400 mA cm−2. This significant flooding blocked reactant sites and contributed to unstable cell performance and, ultimately, cell failure at higher current densities. The SS cell displayed the best water management, with only 11% of the cathode channel filled with water after 1 h at 500 mA cm−2, compared with 28% of the DS cathode channel. 3D visualisation and analysis of droplet behaviour elucidated how water ‘slugs’ in the SS were removed in the gas stream, whereas three of the four parallel cathode flow channels became entirely filled with water plugs, blocking gas flow and exacerbating cell flooding. The new insights gained here are expected to extend to novel flow field designs and image-based models, with the use of operando neutron CT demonstrated as a powerful technique for both visualising and quantifying water management in operating PEFCs, as well as deepening the knowledge of droplet behaviour in different flow field types.

A freely distributable professional computed tomography system using NICOS

Based on the control system of the ANTARES neutron imaging system at FRM II, we have designed a portable, but professional neutron computed tomography system using the same TANGO device servers and the instrument control system NICOS. We have created a minimalistic setup to control a computed tomography setup using a single control computer that directly connects to a camera detector and interfaces a Raspberry Pi computer with motor control board via a local network. The setup has the full capability of a large instrument controller and can control arbitrary hardware (like professional motor controllers) for which hundreds of free drivers are available. Full schematics for the controller as well as print files for 3D printers for the detector housing and disk or virtual machine images are available for free to allow for the quick implementation of a low-cost, but professional neutron CT system even at very low power research reactors.

Neurosensory anatomy and function in Seymouria.

Seymouria is among the best-known stem amniotes and holds an important phylogenetic position for discussions of amniote evolution. Previous work has focused primarily on the osteology of Seymouria, with recent interest turning to the application of computed tomography (CT) to study the internal features. We utilized neutron CT to reconstruct the first virtual cranial endocast and the first complete otic endocasts of Seymouria, revealing previously unrecognized details of its palaeoneuroanatomy. The brain and inner ear of Seymouria are largely plesiomorphic relative to later-diverging crown amniotes, showing no indication of increased encephalization or braincase ossification. Our results also clarify the plesiomorphic condition for carotid artery morphology in amniotes, with Seymouria showing a similar condition to basal members of both the synapsid and sauropsid lineages. The reconstructed neuroanatomy also indicates that Seymouria did not possess any particular neuroanatomical specializations, despite the probable presence of an impedance matching hearing system. This article is protected by copyright. All rights reserved.

An Insight into a Shang Dynasty Bronze Vessel by Nuclear Techniques

A bronze wine vessel attributed to 1600–1046 B.C., Shang dynasty in China, an object from the East Asian Collection of the Museum of Applied Arts and Sciences in Sydney (Australia), was studied using a non-destructive scientific analytical protocol based on the synergic combination of nuclear techniques. Gamma spectrometry, neutron-computed tomography, and proton-induced X-ray emission (PIXE) spectroscopy were applied to gain a better insight into the structural and compositional features of the artefact to prove its authenticity. Gamma spectrometry was performed to assess the risk of excessive sample activation induced by long exposure to the neutron beam and to determine the bulk elemental composition. Based on neutron-computed tomography, the porosities and the thickness of the metal wall were evaluated and found consistent with the piece-mould casting technology adopted by craftsmen during the Shang dynasty in China. Finally, PIXE spectroscopy demonstrated the use of a ternary (copper–tin-leaded) alloy and the nature of mineralisation on the surface.

APPLICATION OF NEUTRON COMPUTED TOMOGRAPHY IN ENHANCED OIL RECOVERY FOR ANALYSING OIL DISTRIBUTION IN BEREA SANDSTONE USING BAGASSE SURFACTANT

The Neutron Computed Tomography (NCT) technique was adopted to study oil content within sandstone. In recent times, oil industries have turned to the Enhanced Oil Recovery (EOR) technique that uses chemicals/surfactants to reduce interfacial tension to maximize oil production from mature oil fields. The Berea core played a crucial role in investigating surfactant effectiveness for liberating trapped oil. The presented research is based on laboratory experiments carried out at the National Research and Innovation Agency and at the Trisakti University, Indonesia. The research proceeded in three steps. The first step was observation on the Berea core that is saturated with a low salinity brine of 40,000 ppm and 60,000 ppm and assessment of the total porosity of the sandstone. The second step included injecting oil into the sample and examining the water distribution. The final step was to inject sugarcane bagasse surfactant with 2% surfactant concentration to extract oil from the sandstone, then it was subjected to NCT analysis. The observations show that the pores are evenly distributed in the middle, the oil content accumulates at the edge, almost no oil remains in the middle of the Berea core after water injection, and the remaining oil returns to the main flow after surfactant injection. The results show that oil movement in the Berea core with 40,000 ppm salinity is better than oil movement with 60,000 ppm. The salinity of the brine can affect the mobility of oil droplets in the Berea core, and surfactant injection processes have better performance at lower salinity and are susceptible to higher salinity.

Neutron tomography of porous aluminum electrodes used in electrocoagulation of groundwater

In this work, neutron computed tomography (CT) is employed to investigate the dissolution of porous aluminum electrodes during electrocoagulation (EC). Porous electrodes were chosen in efforts to reduce electric power requirements by using larger surface-area electrodes, having both inner and outer surface, for the EC process. Neutron CT allowed 3D reconstruction of the porous electrodes, and image analysis provided the volume of each electrode vs. thickness, which can indicate whether the inner surface is effectively involved in EC reactions. For the anode, the volume decreased uniformly throughout the thickness of the electrode, indicating that both the outer and inner surface participated in electrochemical dissolution, while the volume of the cathode increased uniformly vs. thickness, indicating deposition of material on both the outer and inner surface. The attenuation coefficient vs. thickness, increased for both anode and cathode, indicating surface chemistry changes. For the anode, the attenuation coefficient increased slightly but uniformly, probably due to aluminum oxide formation on the surface of the anode. For the cathode, the attenuation coefficient increased more than for the anode and nonuniformly. The higher increase in the attenuation coefficient for the cathode is due to precipitation of aluminum hydroxide on the electrode surface, which added hydrogen. Image analysis also showed that, although the attenuation coefficient increased throughout the thickness of the electrode, most of the hydroxide deposition occurred on the outer surface. Energy analysis showed that porous electrodes can be used to reduce process energy requirements by as much as 4 times compared to solid electrodes.

Nondestructive neutron imaging diagnosis of acidic gas reduction catalyst after 400-Hour operation in natural gas furnace

Residential natural gas furnaces are the primary space-heating devices in US homes, leading to substantial environmental impact caused by the acidic components in the furnace combustion gases. To experimentally demonstrate acidic gas reduction in a furnace, a monolithic catalyst was fabricated and was called the AGR. A commercially-available condensing furnace was retrofitted with the AGR, and a 400-hour reliability and durability test was conducted. The results showed that the AGR significantly reduced acidic gases in the flue gas and produced condensate with neutral pH. Challenges were also revealed: inappropriate condensate drainage caused incomplete combustion and amorphous carbon deposits. To nondestructively survey the internal state of the AGR, neutron computed tomography (NCT) was employed to produce spatially resolved 2D and 3D representations of the 2-L, aged AGR component. The NCT results confirm the integrity of the AGR component, which consists of two blocks, without deformation or damage to AGR channels. The distribution of the particle accumulation in the middle of the top block was visibly heavier than the entrance and exit of the top block. The representative cross-section views revealed significant aggregation in the central region but not at the rim. The spatially resolved details provide in-depth diagnosis, evaluation, and understanding of the AGR. The insights can enable new AGR designs that realize a uniform and self-cleaning flow pattern, alleviate significant particle aggregation, and thus enhance AGR-enabled furnace performance. The neutron imaging method demonstrates the good potential that can diagnose faults and improve the design, optimization, and production processes of novel catalysts and other components or systems with heavy metal shell.

Fused x-ray and fast neutron CT reconstruction for imaging large and dense objects

Megavolt x-ray computed tomography (CT) is a powerful tool for three-dimensional characterization. However, its utility is limited for large objects composed of high-atomic number (Z) materials, where x rays fail to penetrate. Information from fast neutron CT (FNCT) can complement x-ray CT reconstructions since fast neutrons can more readily penetrate high-Z objects. Here, we demonstrate a method for combining FNCT and x-ray CT data to create a single reconstruction, more accurate than could be achieved with either x rays or fast neutrons alone. The algorithm was tested on an exemplar comprising multiple concentric, nested cylinders of different materials. Simulated and empirical x-ray CT data were acquired for the exemplar using a 9 MV bremsstrahlung spectrum. Additional simulated and empirical FNCT data were acquired using an accelerator based fast neutron source. The FNCT data were used to synthesize x-ray CT data and augment the x-ray CT data missing due to lack of penetration. This approach mitigates artifacts that would otherwise negatively affect the accuracy and resolution of a single-modality reconstructed volume.

Investigation of Silicon-Based Anodes for Li-Ion Batteries Using X-Rays and Neutron 3D/4D Imaging Techniques

Silicon-based anode materials are one of the most promising approaches to further increase the energy density of lithium-ion batteries. However, current materials are limited by poor cycling stability and rapid capacity fading, mainly caused by the massive volume expansion of Si during lithiation and subsequent strain on the material composite. [1] Furthermore, this electrode swelling also results in continuous solid electrolyte interface (SEI) growth, which hinders the migration of Lithium and leads to permanent capacity loss. [2] [3]To optimize these materials, analytical techniques able to probe the local 3D morphology and Li content are necessary. By applying methods such as neutron computed tomography (NCT), X-Ray computed tomography (XCT) and synchrotron scattering micro-tomography (SMT) structural ageing and changes in the distribution of lithium in the various components can be characterized and quantified for different charging states and recharge cycle numbers.This study investigates an anode material based on a dual phase alloy system of amorphous Silicon (a-Si) with crystalline iron silicide (c-FeSi2) and graphite. [4] [5] Li-ion battery coin cells containing this silicon-graphite composite anode material were industrially produced and aged by performing 1, 300, and 700 charge-discharge cycles, corresponding to remaining capacities of 100, 70 and 50 %, respectively. NCT and XCT scans were acquired at the NeXT instrument of the ILL in Grenoble (France) [6], and SMT measurements performed at ID31 of the neighboring ESRF. These datasets were reconstructed and evaluated using specially developed data processing pipelines. By performing multi-modal registration, the NCT and XCT scans were aligned and segmented to combine the complementary datasets and create a 4D model of the Li-ion battery coin cells.Figure 1 shows a sample of the combined NCT (cyan) and XCT datasets (red). Cropped horizontal slices of Li-Ion battery coin cells are depicted side by side with the main components labelled. Comparing one of the highly cycled cells with 50% remaining capacity (top) with the reference cell without electrolyte (bottom), trapped Lithium can be observed in the anode layers, visible as cyan colored blotchy areas in the otherwise dark component. The pixel size is approximately 5 µm.The change of lithium distribution in the components between different cycle numbers and charge states in the attenuation-based tomography techniques of NCT / XCT is quantified by modelling expected attenuation parameters to the observed values. The diffraction-based tomography method of SMT was modeled using expected lattice parameters. From this information, trapped Lithium can be identified and changes in the distribution are analyzed to point out possible degradation and failure mechanisms.We acknowledge financial support from the European Union’s Horizon 2020 research and Innovation program No. 875514 (ECO2LIB) as well as No. 847439 (InnovaXN) under the Marie Skłodowska-Curie grant agreement.[1] S. Tardif et al, https://doi.org/10.1021/acsnano.7b05796 [2] T. Vorauer et al, https://doi.org/10.1038/s42004-020-00386-x [3] P. Kumar et al, https://doi.org/10.1002/smll.201906812 [4] C. Berhaut et al, https://doi.org/10.1021/acsnano.9b05055 [5] C. Berhaut et al, https://doi.org/10.1016/j.ensm.2020.04.008 [6] A. Tengattini et al, https://doi.org/10.1016/j.nima.2020.163939 Figure 1

Livermore tomography tools: Accurate, fast, and flexible software for tomographic science

This paper introduces the capabilities and availability of a customizable scientific software package called Livermore Tomography Tools (LTT) built for computed tomography (CT) research. It was initially developed to process x-ray and neutron CT data accurately and rapidly from raw detector counts to reconstructed volumes with the flexibility to handle many special cases. Our goals were to provide quantitatively accurate results reported in physical units (e.g., mm−1 or cm−1) while exploiting all available computational advantages to maximize speed and conserve memory. Written in C/C++ with support for multiple CPUs and GPUs, LTT runs on many computing platforms (Linux/Unix, Windows, and Mac; laptops to supercomputers). As a result, LTT can: process data acquired from various custom-built and commercially available CT scanners, model and simulate x-ray and neutron interactions to encourage algorithm prototyping, and allow for rapid insertion of the latest algorithms. We describe LTT's software architecture, user interfaces, and its 88 algorithms (as of this writing) for pre-processing, reconstruction, post-processing, and simulation that support many scanner geometries (parallel-, fan-, cone-beam, and custom). Several applications are presented that illustrate LTT's accuracy, speed, and flexibility relative to other solutions.

Visualizations of Berea sandstone pores using neutron tomography

Sandstone is a reservoir rock commonly found by oil and gas companies. Oil and gas usually trap inside the sandstone pores. A Destructive-Testing (DT) method or chemical solution method is usually used to measure the porosities of the sandstone sample. On the other hand, neutron computed tomography (NCT) can visualise and quantify all the porosities of the sandstone non-destructively. Neutron tomography is an imaging technique that employs neutron generated by a nuclear research reactor. The NCT produces cross-sectional images of the object that was used to visualise the Barea sandstone porosities distribution. The results show that each rock sample possesses connected and concentrated pores in the middle part of the rock with total porosity of ± 20%.

Convolutional neural network based non-iterative reconstruction for accelerating neutron tomography * * This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce

Neutron computed tomography (NCT), a 3D non-destructive characterization technique, is carried out at nuclear reactor or spallation neutron source-based user facilities. Because neutrons are not severely attenuated by heavy elements and are sensitive to light elements like hydrogen, neutron radiography and computed tomography offer a complementary contrast to x-ray CT conducted at a synchrotron user facility. However, compared to synchrotron x-ray CT, the acquisition time for an NCT scan can be orders of magnitude higher due to lower source flux, low detector efficiency and the need to collect a large number of projection images for a high-quality reconstruction when using conventional algorithms. As a result of the long scan times for NCT, the number and type of experiments that can be conducted at a user facility is severely restricted. Recently, several deep convolutional neural network (DCNN) based algorithms have been introduced in the context of accelerating CT scans that can enable high quality reconstructions from sparse-view data. In this paper, we introduce DCNN algorithms to obtain high-quality reconstructions from sparse-view and low signal-to-noise ratio NCT data-sets thereby enabling accelerated scans. Our method is based on the supervised learning strategy of training a DCNN to map a low-quality reconstruction from sparse-view data to a higher quality reconstruction. Specifically, we evaluate the performance of two popular DCNN architectures—one based on using patches for training and the other on using the full images for training. We observe that both the DCNN architectures offer improvements in performance over classical multi-layer perceptron as well as conventional CT reconstruction algorithms. Our results illustrate that the DCNN can be a powerful tool to obtain high-quality NCT reconstructions from sparse-view data thereby enabling accelerated NCT scans for increasing user-facility throughput or enabling high-resolution time-resolved NCT scans.

Ring artifacts correction based on the projection-field in neutron CT* *Project supported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0401502 and 2017YFB0701903), the National Natural Science Foundation of China (Grant Nos. U1832219 and 12005166), the Youth Innovation Promotion Association, the Chinese Academy of Sciences (CAS) (Grant No. 2017023), the Guangdong Natural Science Foundation, China (Grant

Ring artifacts will happen mostly when the detector has inconsistent response among the detector channels, and the characteristic produced rings centered in the iso-center in the reconstructed slices inevitably affect the recognition and analysis of the corresponding sample structures in neutron computed tomography (CT). In this work, a ring correction method based on the projection-field (RCP) is proposed, it is a pre-processing method and provides the corrected projection data directly, which is also conducive to efficient data storage and other algorithmic researches. Simulation and physical experiments are performed for verifying the effect of the method, and one of the correction methods based on the image-field is used for comparison. The results demonstrate that the RCP can correct the ring artifacts well without reducing the image resolution or over-correction.

Comparison of Thermal Neutron and Hard X-ray Dark-Field Tomography.

High visibility (0.56) neutron-based multi-modal imaging with a Talbot–Lau interferometer at a wavelength of 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 μ. 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.

Lithium Plating Detection in Extremely Fast-Charged Lithium-Ion Batteries Using Simultaneous Neutron and X-Ray Imaging

Lithium-ion batteries (LIBs) have profoundly advanced the development of electric vehicles (EVs). However, one of the remaining bottlenecks in their widespread deployment is the long charging time required for commercial LIBs. Today, there is a global push towards extreme fast charging (XFC) to reduce charging times to 10-15 minutes.1 But existing LIBs cannot achieve this goal without significantly reducing battery performance, mainly due to the loss of active Li. The lost Li either becomes “dead” from being electronically disconnected after plating on the anode or “inactive” because of the irreversible reaction of Li with the electrolyte to form a solid electrolyte interphase. Since lithium plating is identified as one of the major degradation mechanisms from XFC in LIBs,2 understanding its origin and characteristics is essential to developing designs to enable fast-charged batteries. Several studies have characterized Li plating using techniques such as cryo-electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray micro-computed tomography (CT) among others.3 While valuable, these characterization techniques have limitations4 in terms of their sample preparation, spatial resolution, and imaging contrast required to distinguish between materials of similar atomic number (Z). In addition, due to the complex electrochemical reaction mechanisms of Li metal plating, multiple methods for detecting Li metal and understanding the mechanistic details of Li plating are needed.Here, we are using simultaneous neutron and X-ray-based dual-mode micro-computed tomography, a non-destructive imaging modality, to investigate the characteristics of Li plating during XFC in LIBs. Since X-rays and neutrons are sensitive to the electron and nuclear density of the material, respectively, dual-mode X-ray and neutron CT allows the easy separation of the different anode components in a LIB such as Li, graphite, and pores. Higher energy X-rays are needed to get through the metallic components in batteries such as copper and aluminum. However, they do not have sufficient contrast to separate lithium from graphite. Thus, neutrons are used due to their high sensitivity to lighter elements such as lithium, especially 6Li, and carbon.We have performed multi-modal imaging experiments at the Neutron and X-ray Tomography (NeXT)5 system located on the BT-2 beamline at the National Institute of Standards and Technology Center for Neutron Research. We characterized pristine and cycled graphite anode strips containing plated lithium at different regions. For cycled anode strips, we disassembled the battery pouch cells and imaged the graphite anodes cycled under XFC conditions for 450 cycles at fully discharged condition. These strips were used to get sample sizes small enough to achieve the highest possible spatial resolution. The spatial resolution achieved by this technique was ~10-15 μm, thus providing sufficient resolution to pinpoint the location of Li plating within the thickness of the anode. For image processing, we employed bivariate histogram segmentation that uses information from both X-rays and neutrons to segment different anode components. With these dual-imaging datasets, we are now investigating whether a link exists between the spatial heterogeneity of Li metal plating and the local microstructure of the battery anode including porosity, tortuosity, and thickness. We want to investigate why and where Li plating occurs on the battery anode. Addressing these fundamental questions will inform improved battery designs, graphite anode architectures, and charging protocols that will reduce Li plating during XFC in LIBs. Ultimately, these improvements based on our research findings will help make charging an EV similar to filling up at a gas station.

Development of a novel reconstruction method for two-phase flow CT with improved simulated annealing algorithm

Two-phase flow, especially gas-liquid two-phase flow, has a wide application in industrial field. The diagnosis of two-phase flow parameters, which directly determine the flow and heat transfer characteristics, plays an important role in providing the design reference and ensuring the security of online operation of two-phase flow system. Computer tomography (CT) is a good way to diagnose such parameters with imaging method. This paper has proposed a novel image reconstruction method for thermal neutron CT of two-phase flow with improved simulated annealing (ISA) algorithm, which makes full use of the prior information of two-phase flow and the advantage of stochastic searching algorithm. The reconstruction results demonstrate that its reconstruction accuracy is much higher than that of the reconstruction algorithm based on weighted total difference minimization with soft-threshold filtering (WTDM-STF). The proposed method can also be applied to other types of two-phase flow CT modalities (such as X(γ)-ray, capacitance, resistance and ultrasound).

High-Resolution Thermal Neutron Imaging With ¹⁰Boron/CsI:Tl Scintillator Screen

High-resolution neutron imaging is difficult, due to the low-light output of neutron scintillators, and the spread of light within common neutron-sensitive scintillators as well as the spread of intermediate particles occurring during the detection process. To address this issue, we have developed a highresolution scintillator for neutron imaging by combining enriched <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B with the well-known CsI:Tl scintillator films. CsI:Tl has excellent properties for X-ray imaging applications, due to a high light yield of 60 000 photons/MeV, and high spatial resolution, which derives from its microcolumnar structure, which channels scintillation light to the photodetector. To enable CsI:Tl to detect neutrons, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B (96% enriched) was deposited by electron beam directly onto the CsI:Tl film, making a layered scintillator structure in which the alphas produced by the neutron interaction with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B are detected in the CsI:Tl. The <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B layer was approximately 3 μm thick, while the thickness of the CsI:Tl film was 11 μm. These novel layered scintillators were integrated into the high-resolution neutron imaging detector [“Paul Scherer Institute (PSI) Neutron Microscope”] at the Pulse OverLap DIffractometer (POLDI) beamline at the PSI. With our <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B/CsI:Tl scintillator, we were able to achieve a spatial resolution down to 9 μm. To demonstrate the effectiveness of the layered scintillator, we present results obtained by thermal neutron imaging as well as high-resolution neutron-computed tomography. Finally, we believe there is considerable scope for future optimization of the performance of this system.

The structure of scleractinian coral skeleton analyzed by neutron diffraction and neutron computed tomography

Two analytical methods based on the neutrons high penetrability, i.e. neutron diffraction (ND) and neutron computed tomography (NCT) were used to investigate the structure of the aragonitic skeleton of an exemplar/sample of Dipastraea pallida (Dana 1846), a modern hermatypic coral. ND was used to reconstruct the orientation distribution function (ODF) of the crystalline fibrils which compose the coral skeleton. Accordingly, 684 ND spectra were analyzed using the Rietveld method. The result confirmed the aragonite as the sole mineral component of coral skeleton, allowing to recalculate the ODF of aragonite fibrils and to represent it by means of (100), (010) and (001) crystallographic planes pole figures (PF). Experimental PF showed a remarkable similarity with PF recalculated by considering that all aragonite fibrils are oriented either along the growth axis of polyp cups or perpendicular to this direction. This result confirmed the previous observations based on optical microscopy, proving at the same time the availability of ND for such types of investigations. In turn, NCT evidenced the individual polyp cups, their interlocked 3D rigid porous structure as well as a periodic variation of density which could be attributed to a seasonal influence of the marine environment. Different from the classical X-ray computed tomography, the NCT, in view of neutron high cross-section for hydrogen, demonstrated the presence of a small amount of organic matter, otherwise transparent for X- and gamma rays.