Distinguishing differences between authentic artifacts and replicas is a significant challenge in the field of cultural heritage. In this study, we explore the application of neutron grating interferometry and tomography techniques to identify Korean copper coins in the nineteenth century of Joseon period by investigating structural differences between genuine objects and replicas. Neutron grating interferometry provides the microstructural information of coins, including features such as pores and precipitates, through a dark field image derived from small-angle neutron scattering. Additionally, neutron transmission tomography examines the three-dimensional internal structures and potentially hidden features of coins. Both neutron imaging techniques highlight regions that contain lead precipitates in the copper alloy, showing consistent agreement with optical imaging and with the quantitative lead content measured by energy dispersive X-ray spectroscopy. The distinct corrosion patterns observed in the authentic coin and replica provide empirical explanations for the general corrosion mechanism of copper alloy. This interpretation finds support in the moderate contribution of dark field contrast from cuprite, which underlies the signal of lead precipitates.

Two types of anion exchange ionomers, powder and dispersion, are studied in this work. The gas diffusion electrode with the dispersion-type ionomer exhibits strong hydrophobicity, thus not enabling sufficient ionic exchange during the potassium hydroxide exchange process, which in turn exhibits very poor performance. Hence gas diffusion electrode prepared with the powder-type ionomer is used to study the sensitivity and effect of reactant concentration and operating conditions on anion exchange membrane fuel cell performance. The results indicate that the cell performance is most sensitive to relative humidity followed by hydrogen concentration. In contrast, oxygen is not a major performance limiting factor validated by oxygen reactant sensitivity analysis. Results from neutron imaging experiments demonstrate that active water transport from cathode to anode through electro-osmotic drag is very active, which results in flooding on the anode side, causing significant reduction of cell performance. The combined experimental and neutron results provide valuable insight into the water management strategies to improve the stability of fuel cell performance, which has a significant impact towards the development of anion exchange membrane fuel cell.

Heterogeneity in component morphology and distribution, inherent in modern electrochemical devices, frequently limits device performance and durability. However, accurately characterizing heterogeneity is challenging as it requires high-contrast detection of evolving multi-material components and associated interfaces, and this often bottlenecks rational design. In this study, new insights into spatio-operational heterogeneity are quantitatively revealed within multi-component electrochemical systems using simultaneous neutron and X-ray tomography (NeXT). In operando fuel cells, this technique uniquely offers independent yet simultaneous and correlated characterization of material distribution and morphology. This enables accurate contextualization of liquid water within all key component interfaces in sufficient detail to resolve previously unidentified 4D heterogeneity. First, 4D heterogeneity in membrane thickness and water content is found to depend strongly upon location and operating conditions, with membrane thickness variations up to 80 mu m and membrane water content variation from dry to hydrated at 21 . Second, a direct experimental link is established between anisotropic humidification and local anisotropic swelling of the membrane. The observations lend unique insights into degradation mechanisms of the membrane and have notable implications on the practical durability of fuel cells. The proposed methodology is highly relevant to advancing multi-material electrochemical devices (with evidence of applicability to batteries provided).

AbstractWe present a versatile optical setup for high-resolution neutron imaging with an adaptable field of view and magnification that can resolve individual neutron absorption events with an image intensifier and a CMOS camera. Its imaging performance is characterized by evaluating the resolution limits of the individual optical components and resulting design aspects are discussed. Neutron radiography measurements of a Siemens star pattern were performed in event mode acquisition comparing two common high-resolution neutron scintillators, crystalline Gadolinium Gallium Garnet (GGG) and powdered Gadolinium Oxysulfide (GOS). An analysis of the light signature caused by neutron absorption events is performed and some resulting issues for both GGG and GOS regarding optical system design are addressed. Both scintillators reach similar resolution (4–5 $${\upmu }$$ μ m) in event mode acquisition despite different light emission characteristics. The findings suggest that, in the case of GOS, the resolution is limited by the size of the light clusters which in turn originate from the photon scattering at the boundaries of the powder particles comprising it, while with GGG the lower light conversion efficiency makes it challenging to collect enough photons to trigger sufficient signal amplification in the image intensifier. Overall, the proposed event-based evaluation of scintillators allows for quantifying and optimizing various design parameters, which is much more complex than adopting conventional methods based on integrated images.

We have analysed, through neutron diffraction experiments with the volume-gauge technique, the operando performance of lead cells composed of industrial positive and negative electrodes, previously tank formed in the manufacturing plant. The cells, 6.7 cm x 11.5 cm in surface, comprised a 3.4 mm thick positive electrode sandwiched between two 2.3 mm thick negative electrodes. The electrolyte was sulphuric acid diluted in water, both deuterated, and the separators were industrial grade absorptive glass mat (AGM). The experiments, carried out using the VULCAN instrument at the Oak Ridge National Laboratory (TN, USA), showed the evolution of alpha-PbO2, beta-PbO2 and PbSO4 phases in the positive active mass during charge/discharge cycling, comparing the behaviour of fresh and cycled cells. No evidence of PbSO4 phase in fully charged plates or PbO in any state of charge were found above 1% by weight. Significant inhomogeneity of phase distribution and transition rates inside the positive electrode was observed. The experiments allowed estimation of the energy efficiency by comparing the external energy provided to the cell with the energy stored in the PbSO4 to PbO2 transformations.

Phase-grating moiré interferometers (PGMIs) have emerged as promising candidates for the next generation of neutron interferometry, enabling the use of a polychromatic beam and manifesting interference patterns that can be directly imaged by existing neutron cameras. However, the modeling of the various PGMI configurations is limited to cumbersome numerical calculations and backward propagation models which often do not enable one to explore the setup parameters. Here we generalize the Fresnel scaling theorem to introduce a k-space model for PGMI setups illuminated by a cone beam, thus enabling an intuitive forward propagation model for a wide range of parameters and experimental setups. The interference manifested by a PGMI is shown to be a special case of the Talbot effect, and the optimal fringe visibility is shown to occur at the moiré location of the Talbot distances. We derive analytical expressions for the contrast and the propagating intensity profiles in various conditions and provide the first analysis of the PGMI dark-field imaging signal when considering sample characterization. The model's predictions are compared to experimental measurements and good agreement is found between them. Last, we propose and experimentally verify a method to recover contrast at typically inaccessible PGMI autocorrelation lengths. The presented work provides a toolbox for analyzing and understanding existing PGMI setups and their future applications, for example extensions to two-dimensional PGMIs and characterization of samples with nontrivial structures. Published by the American Physical Society 2024

Neutron interferometry has played a distinctive role in fundamental science and characterization of materials. Moiré neutron interferometers are candidate next-generation instruments: they offer microscopy-like magnification of the signal, enabling direct camera recording of interference patterns across the full neutron wavelength spectrum. Here we demonstrate the extension of phase-grating moiré interferometry to two-dimensional geometries. Our fork-dislocation phase gratings reveal phase singularities in the moiré pattern, and we explore orthogonal moiré patterns with two-dimensional phase-gratings. Our measurements of phase topologies and gravitationally induced phase shifts are in good agreement with theory. These techniques can be implemented in existing neutron instruments to advance interferometric analyses of emerging materials and precision measurements of fundamental constants.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation I. Hidrovo, J. Dey, H. Meyer, D. S. Hussey, N. N. Klimov, L. G. Butler, K. Ham, W. Newhauser; Erratum: "Neutron interferometry using a single modulated phase grating" [Rev. Sci. Instrum. 94, 045110 (2023)]. Rev. Sci. Instrum. 1 April 2024; 95 (4): 049903. https://doi.org/10.1063/5.0206178 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioReview of Scientific Instruments Search Advanced Search |Citation Search

Neutron interferometry uniquely combines neutron imaging and scattering methods to enable characterization of multiple length scales from 1 nm to 10 µm. However, building, operating, and using such neutron imaging instruments poses constraints on the acquisition time and on the number of measured images per sample. Experiment time-constraints yield small quantities of measured images that are insufficient for automating image analyses using supervised artificial intelligence (AI) models. One approach alleviates this problem by supplementing annotated measured images with synthetic images. To this end, we create a data-driven simulation framework that supplements training data beyond typical data-driven augmentations by leveraging statistical intensity models, such as the Johnson family of probability density functions (PDFs). We follow the simulation framework steps for an image segmentation task including Estimate PDFs → Validate PDFs → Design Image Masks → Generate Intensities → Train AI Model for Segmentation. Our goal is to minimize the manual labor needed to execute the steps and maximize our confidence in simulations and segmentation accuracy. We report results for a set of nine known materials (calibration phantoms) that were imaged using a neutron interferometer acquiring four-dimensional images and segmented by AI models trained with synthetic and measured images and their masks.

The interrogation of materials with X-rays or neutrons to determine structure, energetics, and dynamics is fundamental to advancing physical and chemical materials science and enabling innovative material technologies. A persistent challenge in materials development is that progress depends on understanding structure and dynamics across multiple length and time scales in increasingly complex, multicomponent systems featuring interfaces, heterogeneity, and hierarchical organization. Despite rapidly growing demands on materials characterization, current experimental approaches are almost exclusively based on isolated X-ray or neutron scattering and spectroscopy, reflecting a paradigm largely unchanged for decades. To assess the scientific need for a new experimental paradigm, a 3-day workshop sponsored by the U.S. National Science Foundation (NSF) was held at the SpringHill Suites, San Jose, California, from June 2 to 4, 2022. The workshop brought together 70 national and international experts who critically evaluated opportunities enabled by concurrent neutron and X-ray (NeX) scattering, spectroscopy, and imaging experiments. The participants reached a clear consensus that establishing NeX capabilities is crucial for advancing the science of complex materials in the United States. This report illustrates the scientific drivers for NeX experiments through representative examples spanning biomaterials, energy materials, soft matter, nanomaterials, quantum materials, geoscience, and applied materials research. The complementarity of neutrons and X-rays is essential for robust model development and refinement, particularly in multiphase and multicomponent systems. While joint refinement of data from separate experiments is valuable, concurrent measurements uniquely eliminate uncertainties arising from sample evolution, environmental drift, and irreproducibility associated with experiments performed at different locations and times. Realizing NeX capabilities will require the development of new instrumentation, data analysis frameworks, and robust sample environments compatible with both neutron and X-ray probes. Addressing these challenges will enable unambiguous interpretation of complex materials behavior and open new frontiers in materials research.

In this study, we offer a complete investigation of a high-performing Proton Exchange Membrane Fuel Cell stack customized for automotive use. Our approach goes beyond traditional global electrochemical performance metrics such as polarization curves, ohmic resistance. Instead, we utilize specialized segmented high-surface sensors to measure current density and temperature in the active area plane, along with neutron imaging to determine liquid water distributions. Employing a pseudo three-dimensional two-phase flow model that integrates electrochemical and transport phenomena, we gain insight into the intricate relationships among these observables. The model proves particularly valuable in elucidating the operation of the anode and cathode sides, aspects challenging to capture solely through experimental mean. Our findings emphasize the substantial impact of fluid flow directions and current density on the distribution of liquid water. It is noteworthy that despite fluid flow direction, there is a consistent decrease in overall liquid water content with an increase in current density. This results in voltage instability within the cell, attributed to flooding phenomena, especially at low current densities. However, this is not observed in conditions representative of those encountered in on-field systems. We conduct a thorough analysis of this failure scenario to improve the fuel cell system’s control mechanisms.

Hierarchical structures and heterogeneous materials are found in many natural and engineered systems including additive manufacturing, alternative energy, biology and polymer science. Though the structure–function relationship is important for developing more advanced materials, structural characterization over broad length scales often requires multiple complementary measurements. Neutron far-field interferometry aims to enable multi-scale characterization by combining the best of neutron imaging with small-angle neutron scattering (SANS) via dark-field imaging. The microstructure, nominally from 1 nm to 10 µm, is averaged over each volume element ∼(50 µm) 3 in the sample, resulting in a `tomographic SANS' measurement. Unlike in small-angle scattering, there are few analytical models to fit dark-field imaging data to extract properties of the microstructure. Fortunately, the dark field and SANS are related through a single Hankel transform. In this work, we discuss the development of a Python-based library, correlogram-tools , that makes use of existing small-angle scattering models and a numerical implementation of the Hankel transform to simulate dark-field interferometry data. We demonstrate how this software can be used to inform researchers of viable sample sets for interferometry experiments, analyze interferometry data, and simulate raw and reconstructed interferometry images for the training of more advanced segmentation models and analysis protocols.

Ghost Imaging enables 2D reconstruction of an object even though particles transmitted or emitted by the object of interest are detected with a single pixel detector without spatial resolution. This is possible because for the particular implementation of ghost imaging presented here, the incident beam is spatially modulated with a non-configurable attenuating mask whose orientation is varied (e.g. via transverse displacement or rotation) in the course of the ghost imaging experiment. Each orientation yields a distinct spatial pattern in the attenuated beam. In many cases, ghost imaging reconstructions can be dramatically improved by factoring the measurement matrix which consists of measured attenuated incident radiation for each of many orientations of the mask at each pixel to be reconstructed as the product of an orthonormal matrix Qand an upper triangular matrix R provided that the number of orientations of the mask (N) is greater than or equal to the number of pixels (P) reconstructed. For the N<P case, we present a data augmentation method that enables QR factorization of the measurement matrix. To suppress noise in the reconstruction, we determine the Moore-Penrose pseudoinverse of the measurement matrix with a truncated singular value decomposition approach. Since the resulting reconstruction is still noisy, we denoise it with the Adaptive Weights Smoothing method. In simulation experiments, our method outperforms a modification of an existing alternative orthogonalization method where rows of the measurement matrix are orthogonalized by the Gram-Schmidt method. We apply our ghost imaging methods to experimental X-ray fluorescence data acquired at Brookhaven National Laboratory.

The continued advancement of complex materials often requires a deeper understanding of the structure-function relationship across many length scales, which quickly becomes an arduous task when multiple measurements are required to characterize hierarchical and inherently heterogeneous materials. Therefore, there are benefits in the simultaneous characterization of multiple length scales. At the National Institute of Standards and Technology, a new neutron far-field interferometer is under development that aims to enable a multi-scale measurement combining the best of small-angle neutron scattering (SANS) and neutron imaging and tomography. Spatially resolved structural information on the same length scales as SANS (0.001-1 mu m) and ultra-small-angle neutron scattering (USANS, 0.1-10 mu m) will be collected via dark-field imaging simultaneously with regular attenuation radiography (>10 mu m). The dark field is analogous to the polarization loss measured in spin-echo SANS (SESANS) and is related to isotropic SANS through a Hankel transform. Therefore, we use this close relationship and analyze results from SANS, USANS, SESANS and dark-field imaging of monodisperse spheres as a validation metric for the interferometry measurements. The results also highlight the strengths and weaknesses of these neutron techniques for both steady-state and pulsed neutron sources. Finally, we present an example of the value added by the spatial resolution enabled by dark-field imaging in the study of more complex heterogeneous materials. This information would otherwise be lost in other small-angle scattering measurements averaged over the sample.

Neutron radiography has been a powerful tool for measuring water content within operating fuel cells. The resolution for neutron imaging has been steadily improving and has demonstrated the ability to measure water content in industrially relevant catalyst layers. The difficulty in measuring catalyst layer or interfacial water content with neutron radiography is that the method assumes that the layers of the MEA are flat and uniform with no variation which is a poor assumption. To combat this assumption, it is necessary to move to neutron tomography that resolves the fuel cell in three dimensions. Combining neutron tomography with simultaneous X-ray tomography improves layer and interface identification which facilitates better water saturation measurements. In addition to capturing the “waviness” of the MEA, this method can be applied to tracking water distribution in structured 3D electrodes. This talk will demonstrate current developments in fast simultaneous neutron and X-ray tomography, methods to improve saturation calculations within the various porous layers, and showcase new hardware developments available to the NIST user community.

Electrolysis is a critical component to realizing a true green hydrogen economy. The performance and efficiency of an electrolyzer is directly tied to the multiphase transport that occurs within the porous transport layer (PTL). The PTLs must allow sufficient water transport to the catalyst layer to maintain the reaction while removing the product gases. PTLs are typically created from titanium foams or sintered from titanium powders or fibers. The resultant structure is heterogenous and requires 3D imaging to properly capture the pore structure and transport pathways. The use of titanium for the PTL can make it difficult to track the multiphase flow using X-rays alone as the X-ray energy required to penetrate 1 cm or more reduces the contrast between water and oxygen without the use of contrast agents that could affect the reaction. Neutrons provide a penetrating probe capable of imaging through titanium while having extreme sensitivity to water. Combing neutrons and high energy X-rays provides an easy way to identify all components in the PTL, i.e., the solid structure, oxygen, and water. The National Institute of Standards and Technology provides the Neutron Imaging Facility to the larger research community through the Center for Neutron Research facility user program. This instrument provides the ability to perform simultaneous neutron and X-ray tomography. Moving from 2D radiography to 3D tomography is critical to fully understand the influence of the PTL pore structure on the multiphase transport. This talk will give an overview of the instrument capabilities, showcase past success for neutron imaging of electrolyzers, and provide current progress on development of hardware and data reduction methods for simultaneous neutron and X-ray tomography of electrolyzers.

Neutron grating interferometry provides information on phase and small-angle scatter in addition to attenuation. Previously, phase grating moiré interferometers (PGMI) with two or three phase gratings have been developed. These phase-grating systems use the moiré far-field technique to avoid the need for high-aspect absorption gratings used in Talbot-Lau interferometers (TLI) that reduce the neutron flux reaching the detector. We first demonstrate, through theory and simulations, a novel phase grating interferometer system for cold neutrons that requires a single modulated phase grating (MPG) for phase-contrast imaging, as opposed to the two or three phase gratings in previously employed PGMI systems. The theory shows the dual modulation of MPG with a large period and a smaller carrier pitch P, resulting in large fringes at the detector. The theory was compared to the full Sommerfeld-Rayleigh diffraction integral simulator. Then, we proceeded to compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with best-case visibility of around 39%. The simulations of the MPG system show improved visibility in comparison to that of the two-phase-grating-based PGMI. An MPG with a modulation period of 300 µm, the pitch of 2 µm, and grating heights with a phase modulation of (π,0, illuminated by a monochromatic beam produces visibility of 94.2% with a comparable source-to-detector distance (SDD) as the two-phase-grating-based PGMI. Phase sensitivity, another important performance metric of the grating interferometer, was compared to values available in the literature, viz. the conventional TLI with the phase sensitivity of 4.5 × 103 for an SDD of 3.5 m and a beam wavelength of 0.44 nm. For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 × 103 to 10.0 × 103 for SDDs of up to 3.5 m. This proposed MPG system appears capable of providing high-performance PGMI that obviates the need for the alignment of two phase gratings.

We discuss instrumentation and analysis efforts at NIST to develop neutron dark-field imaging, simultaneous neutron/X-ray tomography and the Wolter optics neutron microscope. Progress will be highlighted through applications in electrochemistry, advanced manufacturing, concrete, and geology.

This study aims to determine an acquisitional and computational workflow that yields the highest quality spatio-spectral reconstructions in four-dimensional neutron tomography studies. The properties of neutrons enable unique image contrast modes, but accessing these modes requires defining the energy of the neutron beam, resulting in long acquisition times. We seek sparse angular tomography approaches to collect of order 100 tomograms at different neutron wavelengths using the minimum number of input projection images. In these computational image workflows, we identified and evaluated the main factors affecting the quality of the tomographic reconstruction such as the projection number, the reconstruction method, and the post-processing method and we report relationships between 3D reconstruction quality metrics and acquisition time. Based on these relationships, the performance of seeded simultaneous iterative reconstruction-based techniques (SIRT and SIRT with total variation regularization) yielded improved image quality and more accurate estimates of the reconstructed attenuation values compared to other methods, which included convolutional neural networks. The methods were then applied to a dose-reduced monochromatic dataset and characterized via signal-to-noise ratio (SNR) and single-voxel resolution.

Dark-field imaging probes the projected autocorrelation function at the autocorrelation length of the grating interferometer and quantitatively accesses the parameters of a microstructure model. The National Institute of Standards and Technology has developed a novel far-field grating interferometer to study hierarchical materials in various fields such as polymer science, geology, additive manufacturing under the INFER project. In this work, we detail the simulation of dark-field imaging which is one of the goals of INFER.