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Understanding the complicated interplay of the continuously evolving electrode materials in their inherent 3D states during the battery operating condition is of great importance for advancing rechargeable battery research. In this regard, the synchrotron X-ray tomography technique, which enables non-destructive, multi-scale, and 3D imaging of a variety of electrode components before/during/after battery operation, becomes an essential tool to deepen this understanding. The past few years have witnessed an increasingly growing interest in applying this technique in battery research. Hence, it is time to not only summarize the already obtained battery-related knowledge by using this technique, but also to present a fundamental elucidation of this technique to boost future studies in battery research. To this end, this review firstly introduces the fundamental principles and experimental setups of the synchrotron X-ray tomography technique. After that, a user guide to its application in battery research and examples of its applications in research of various types of batteries are presented. The current review ends with a discussion of the future opportunities of this technique for next-generation rechargeable batteries research. It is expected that this review can enhance the reader's understanding of the synchrotron X-ray tomography technique and stimulate new ideas and opportunities in battery research.

The neutron imaging instrument CONRAD was operated as a part of the user program of the research reactor BER-II at Helmholtz-Zentrum Berlin (HZB) from 2005 to 2020. The instrument was designed to use the neutron flux from the cold source of the reactor, transported by a curved neutron guide. The pure cold neutron spectrum provided a great advantage in the use of different neutron optical components such as focusing lenses and guides, solid-state polarizers, monochromators and phase gratings. The flexible setup of the instrument allowed for implementation of new methods including wavelength-selective, dark-field, phase-contrast and imaging with polarized neutrons. In summary, these developments helped to attract a large number of scientists and industrial customers, who were introduced to neutron imaging and subsequently contributed to the expansion of the neutron imaging community.

Porous carbon felts (CFs) are widely used electrode materials for vanadium redox flow batteries (VRFBs). These materials differ in their precursor material, thickness, or graphitization degree and demonstrate broad differences in electrochemical performance. Prior to operation, an activation step, such as acid or heat treatment (HT), is commonly performed to improve their performance. A thermal treatment in air functionalizes the surface of the electrode and improves reaction kinetics as well as the wettability of the electrode. Herein, pristine and heat‐treated CFs are compared regarding their electrolyte wetting behavior for the use in VRFB. Contact angle (CA) measurements are conducted ex situ to investigate the effect of the HT. Furthermore, the porous CFs are examined in situ with an in‐house‐built flow cell regarding their invasion behavior with different types of electrolytes by X‐ray radiography. Additionally, the distribution of the electrolyte inside the felts is investigated by X‐ray tomography. The results demonstrate the effect of the HT and choice of electrolyte on the wetting behavior and electrolyte distribution.

Knowledge about degradation and failure of Li ion batteries LIBs is of paramount importance, especially because failure can be accompanied by severe hazards. To contribute to the understanding of such phenomena, synchrotron in line phase contrast X ray tomography was employed to investigate internal cell deformation and degradation caused by an internal short circuit ISC . The tomographic images taken from an uncycled Li Li cell and a short circuited Li Li cell reveal how lithium microstructures LmSs develop during electrochemical stripping and plating during discharge and charge and how the three layer separator used is damaged by growing LmSs and delaminates and melts as a consequence of an ISC. Previously unknown insights into the internal cell degradation and deformation mechanisms caused by an ISC are obtained and provide hints of how the properties of the separator could be modified to improve the reliability and safety of current and next generation LIBs

Two kinds of prototypes of lithium ion batteries (LIBs) for in situ X-ray tomography and radiography are reported. Tomography cells (tomo-cells) and radiography cells (radio-cells) both assembled with silicon/carbon (Si/C) or tin/carbon (Sn/C) working electrodes and Li counter electrodes were investigated with synchrotron X-ray and laboratory X-ray imaging. The structural changes of individual electrode particles during charging and discharging were analyzed. Here we are providing a brief overview to our recent results on this field.

The construction of the new neutron imaging instrument at the BER-2 research reactor of the Helmholtz-Zentrum Berlin has greatly increased the potential of the facility. The redesign of the facility included improvements of the neutron extraction and transportation systems, more effective shielding, and innovative instrumentation. The cold neutron flux at the neutron guide exit was increased by more than one order of magnitude, which allowed for an implementation of methods that require monochromatic or polarized beams, thus enabling the exploitation of nonconventional contrast mechanisms such as phase, diffraction and magnetic contrasts. The improved instrument design also facilitates the development of high-resolution neutron tomography by providing an increased beam intensity at the sample position.

A strategy to mitigate typical reconstruction artefacts in missing wedge computed tomography is presented. These artefacts appear as elongations of reconstructed details along the mean direction (i.e. the symmetry centre of the projections). Although absent in standard computed tomography applications, they are most prominent in advanced electron tomography and also in special topics of X-ray and neutron tomography under restricted geometric boundary conditions. We investigate the performance of the DIRECTT (Direct Iterative Reconstruction of Computed Tomography Trajectories) algorithm to reduce the directional artefacts in standard procedures. In order to be sensitive to the anisotropic nature of missing wedge artefacts, we investigate isotropic substructures of metal foam as well as circular disc models. Comparison is drawn to filtered backprojection and algebraic techniques. Reference is made to reconstructions of complete data sets. For the purpose of assessing the reconstruction quality, Fourier transforms are employed to visualize the missing wedge directly. Deficient reconstructions of disc models are evaluated by a length-weighted kernel density estimation, which yields the probabilities of boundary orientations. The DIRECTT results are assessed at different signal-to-noise ratios by means of local and integral evaluation parameters.

The potentials of incoherent X-ray scattering (Compton) computed tomography (CT) are investigated. The imaging of materials of very different atomic number or density at once is generally a perpetual challenge for X-ray tomography or radiography. In a basic laboratory set-up for simultaneous perpendicular Compton scattering and direct beam attenuation tomography are conducted by single channel photon counting line scans. This results in asymmetric distortions of the projection profiles of the scattering CT data set. In a first approach, corrections of Compton scattering data by taking advantage of rotational symmetry yield tomograms without major geometric artefacts. A cylindrical sample composed of PE, PA, PVC, glass and wood demonstrates similar Compton contrast for all the substances, while the conventional absorption tomogram only reveals the two high order materials. Comparison to neutron tomography reveals astonishing similarities except for the glass component (without hydrogen). Therefore, Compton CT offers the potential to replace neutron tomography, which requires much more efforts.

Kurzfassung Typische „Missing Wedge“(MW)-Artefakte in Rekonstruktionen der Computertomografie können mit dem iterativen DIRECTT-Algorithmus (Direkte iterative Rekonstruktion computertomografischer Trajektorien) unterdrückt werden. Die durch fehlende Projektionswinkel bedingten MW-Restriktionen betreffen bisher nur Sonderapplikationen der Röntgen- und Neutronentomografie, müssen in der Nanometer auflösenden Elektronentomografie jedoch als Standard akzeptiert werden. Die MW-Artefakte werden besonders effektiv mit einer spezifischen DIRECTT-Prozedur partiell diskreter Zwischenlösungen beseitigt. Für die Beurteilung der Abbildungsqualität werden Rekonstruktionen von vollständigen und unvollständigen Mess- und Modell-Datensätzen erzeugt und mit Ergebnissen anderer Algorithmen (gefilterte Rückprojektion (FBP) und ART-Methoden) verglichen. Die Fourier-Transformierten der Rekonstruktionen demonstrieren die erfolgreiche Ergänzung der fehlenden Information im MW-Bereich. Die quantitative Bewertung der lokalen Rekonstruktionsqualität mit Methoden der räumlichen Statistik ergibt auch für unterschiedliche Signal-Rausch-Verhältnisse signifikante Vorteile gegenüber FBP und ART.

We present a synchrotron X-ray tomographic study on the morphology of carbon fiber-based gas diffusion layer (GDL) material under compression. A dedicated compression device is used to provide well-defined compression conditions. A flat compression punch is employed to study the fiber geometry at different degrees of compression. Transport relevant geometrical parameters such as porosity, pore size and tortuosity distributions are calculated. The geometric properties notably change upon compression which has direct impact on transport conditions for gas and fluid flow. The availability of broad 3D paths, which are most important for the transport of liquid water from the catalyst layer through the GDL, is markedly reduced after compression. In a second experiment, we study the influence of the channel-land-pattern of the flow-field on shape and microstructure of the GDL. A flow-field compression punch is employed to reproduce the inhomogeneous compression conditions found during fuel cell assembly. While homogenously compressed underneath the land the GDL is much less and inhomogeneously compressed under the channel. The GDL material extends far into the channel volume where it can considerably influence gas and fluid flow. Loose fiber endings penetrate deeply into the channel and form obstacles for the discharge of liquid water droplets.

The imaging facility at the BER II reactor was designed in 2004 and constructed in 2005 as an instrument supporting the materials research activities at the former HMI (department SF3). At that tim...

Nondestructive 3D mapping of crystallographic phases is introduced providing distribution of phase fractions within the bulk (centimeter range) of samples with micrometer-scale resolution. The novel neutron tomography based technique overcomes critical limitations of existing techniques and offers a wide range of potential applications. It is demonstrated for steel samples exhibiting phase transformation after being subjected to tensile and torsional deformation.

Conservation of cultural heritage is extremely important not only from a cultural point of view, but also from a practical one. It is our duty to pass on to future generations the cultural heritage left to us by our ancestors. Wood is one of the most common materials used to generate works of art which are in a state of constant change and/or deterioration. In order to optimize the knowledge of artworks together with their conservation, it is necessary to use the most advanced scientific and technological tools. In the following paper, we will show the tomographic results which can be achieved by application of complementary techniques based on the combined use of X-ray and neutron radiography as structural probes.

The potential of wavelength resolved neutron transmission experiments is well known. This paper is focused on the performance of the double crystal monochromator which is widely used at steady state neutron sources and compares simulation results based on neutron ray tracing with experimental results in order to provide a better understanding of the device. The influences of crystal mosacities on the neutron beam is reported for the utilised setup and the resulting wavelength gradients along one direction are determined. For the neutron imaging geometry applied, a wavelength gradient of about 0.005 A/cm at the sample position was found. Moreover, a new neutron radiography technique for Bragg edge mapping in imaging experiments utilising a neutron wavelength gradient at the sample position was developed and is reported. Experiments and simulations are found to be in good agreement.

Nano-structuring of active materials is a promising way to enhance the performance of Li-ion batteries regarding electronic properties, charge transfer during cycling as well as the resistance to mechanical stress. Moreover, producing thicker electrodes, i.e. thicker than 100 μm, leads to an increase in energy density of the cell and to a reduction of costs. In the present paper, thin and thick electrodes are compared, each manufactured with nano-structured and bulk active material, respectively. The focus is on their 3D microstructure, which is, in turn, important for the performance of the battery. Experimental approaches are combined with statistical image analysis based on synchrotron tomography. In general the results obtained by experiments are in good accordance with the ones obtained by image analysis. Moreover, image analysis allows for the computation of characteristics that are experimentally not accessible. In particular, the system of particle midpoints, the local volume fraction of active material at certain distances to the current collector foil, as well as the windedness and narrow constrictions of transportation pathways are analyzed using tools from spatial statistics and mathematical morphology. The main result is that the considered microstructure characteristics depend only slightly on the thickness of the electrode, while significant differences can be observed between electrodes manufactured with nano-structured and bulk active material.

We herein report on using a compact and low cost scintillator-camera based neutron detection system for quantitative time-of-flight imaging applications. While powerful pulsed neutron sources emerge and enable unprecedented scientific achievements, one bottleneck is the availability of suitable detectors that provide high count- and high frame- rate capabilities. For imaging applications the achievable spatial resolution/pixel size is obviously another key characteristic. While major effort was so far directed towards the development of neutron counting type imaging detectors, this work demonstrates that a camera based detector system as commonly employed at steady state sources can also be used if a suitable camera is utilized. This is demonstrated at the ESS test beamline (V20) at Helmholtz-Zentrum Berlin by recording the time-of-flight transmission spectrum of steel samples using a CMOS camera at 1 kHz frame rate, revealing the characteristic Bragg edge pattern. This 'simple' setup in the current state presents a useful option of neutron detection and has the potential to overcome many of the existing limitations and could provide a reliable alternative for neutron detector technology in general, given that the camera and scintillator technology keep up the current development speed.

Spin-echo modulation small-angle neutron scattering (SEMSANS) is based on the detection of spatial beam modulation, which is induced by triangular spin echo precession regions and subsequent spin analyses. In order to detect such signal and exploit it for small angle scattering investigations neutron detection with sub-millimeter spatial resolution is required. Here an approach is reported where instead of a position sensitive detector an absorption grating is used to analyze the beam modulation stepwise. The spin-echo length scan in this case is performed by varying the sample-to-detector distance. The real space correlation functions of reference sample structures in the range 10(2) nm, i.e. giving rise to small-angle scattering in the very small-angle range, are recorded and analyzed successfully. (C) 2012 Elsevier B.V. All rights reserved. (Less)

Energy dependent neutron transmission imaging has recently gained attention for the potential to spatially resolve texture, crystallographic phase and lattice strain. Especially promising is the time-of-flight (TOF) approach that takes maximum advantage of the new generation of pulsed spallation neutron sources, such as SNS, JSNS and ESS. In this paper, the authors demonstrate the feasibility to efficiently apply the TOF approach at a continuous source in order to spatially resolve and quantify the (lattice) strain distribution in a flat steel sample under tensile loading. Although transmission-based TOF imaging for strain mapping at a pulsed source is well published, this work is the first attempt to demonstrate such measurement using choppers at a continuous neutron source. A critical component for spatially resolved TOF imaging is the availability of a high spatial resolution imaging detector, capable of the required time resolution. For the herein presented work, a conventional 2D position-sensitive 3 He detector with a spatial resolution of 2×3 mm 2 has been used for proof-of-principle measurements. The results are compared to conventional lattice strain measurements obtained at an engineering neutron diffractometer, where the same mechanical loading system was utilized. The efficiency of the time-of-flight transmission method is discussed with respect to other methods, at continuous as well as at pulsed sources.

Cold neutrons have a wavelength that is in the same range as the lattice spacings of most polycrystalline metallic materials. Imaging of such materials with monochromatic cold neutrons of different wavelengths provides a unique contrast due to coherent Bragg scattering. Additionally, the spectral positions of the Bragg edges can be mapped for each point of an image by using the transmission data of corresponding wavelength scans. We present investigations of welded components with such energy-selective neutron radiography around specific Bragg-edges in the transmission spectrum. Features in the local microstructure of the weld have been visualized.

We present two different methods to increase the size of available neutron beams in order to allow for the investigation of large objects. Application of these methods is demonstrated for radiographic imaging of fuel cells. The first approach is a scanning procedure based on the coordinated translation of detector and sample through the beam. Further advancement was achieved by installing a focusing neutron guide, which offers an expanded neutron beam size after diverging from a focused point source.

An optimized detector system that allows high-resolution neutron imaging with desired flexibility is described. The presented system can be adapted and integrated with standard CCD-based neutron detectors. Novel neutron scintillating materials with good photon discrimination and optical lens components are tested and optimized for high-resolution neutron tomographic purposes. The presented detector system provides variable field of view and can be used in combination with different techniques, including dark-field, energy-selective, and neutron spin polarized imaging.

We present the use of helium-3 spin filters for polarized neutron imaging of magnetic phenomena. These polarization devices allow improvements in both spatial (factor of 2–3) and temporal (factor of ∼5) resolution compared with previously used solid-state benders. This set-up has been used to visualize small-scale magnetic features in an Fe 65.7 Co 18 Si 0.8 B 15.5 foil with a thickness of 21–22 μm and a saturation magnetization of 1.7 T, and trapped magnetic flux in a superconducting lead cylinder.

Energy resolved imaging has recently gained attention for the potential of spatially resolved texture, crystallographic phase and strain investigations. Especially a time-of-flight (TOF) approach that takes maximum advantage of the new generation of pulsed spallation neutron sources is currently in the focus of investigations. Here, we present results of corresponding TOF measurements recorded at the continuous source of Helmholtz Center Berlin. The critical component for TOF imaging is however the availability of a high resolution imaging detector capable of the required time resolution. Here, a gated time-integrating detector without the corresponding continuous time resolution has been used and the measurements therefore have to be interpreted as proof-of-principle experiments as will be discussed. Measurements of different series of samples revealing structural differences related to their crystalline structure will be presented as well as a strain measurement on a dieless drawn wire.

During the last decade neutron imaging has seen significant improvements in instrumentation, detection and spatial resolution. Additionally, a variety of new applications and methods have been explored. As a consequence of an outstanding development nowadays various techniques of neutron imaging go far beyond a two- and three-dimensional mapping of the attenuation coefficients for a broad range of samples. Neutron imaging has become sensitive to neutron scattering in the small angle scattering range as well as with respect to Bragg scattering. Corresponding methods potentially provide spatially resolved and volumetric data revealing microstructural inhomogeneities, texture variations, crystalline phase distributions and even strains in bulk samples. Other techniques allow for the detection of refractive index distribution through phase sensitive measurements and the utilization of polarized neutrons enables radiographic and tomographic investigations of magnetic fields and properties as well as electrical currents within massive samples. All these advanced methods utilize or depend on wavelength dependent signals, and are hence suited to profit significantly from pulsed neutron sources as will be discussed.

The ability to resolve the wavelength in neutron transmission experiments has opened up a wide range of applications investigating crystallographic structures and properties. The investigations presented in this paper apply the Bragg edge transmission technique to the study of texture in a cylindrical aluminium specimen. The feasibility of this method is the main focus of this work; hence, conventional pole-figure measurements have been conducted with neutron diffraction to provide reference data for the evaluation of the transmission results. Furthermore, a Monte Carlo simulation has been developed to emulate the experimental conditions and allow investigations of instrument effects. The results have been compared and are discussed with respect to quantitative texture analysis.

Polarized neutron imaging has recently been introduced as an efficient method to three-dimensionally visualize and measure magnetic fields even in the bulk of massive objects. Here we introduce a spin-echo approach for polarized neutron imaging, which has the potential to overcome some drawbacks of the first attempts, namely to deal with strong fields, arbitrary field directions and quantification. Furthermore our novel approach increases the efficiency of quantitative studies due to relaxed monochromatisation requirements for spin-echo neutron imaging and with respect to additional information available in the recorded images, which allows for straightforward quantification in many cases.

Neutron radiography is increasingly being considered a powerful diagnostic tool in fuel cell research. Analyzing the water distribution for entire cells requires large and flexible fields of view and high spatial resolution at the same time. The combination of these requirements is a great technical challenge for neutron detectors: While conventional detectors could provide large fields of view, the accuracy of water mapping has so far been limited by their low spatial resolution. On the other hand, the applicability of sophisticated high-resolution detectors in fuel cell research is limited by their small and invariable fields of view. We present a novel detector system designed to meet the specific demands of fuel cell research. High spatial resolution of at the best 25 μm was achieved by an optimized gadox scintillator, while a large and flexible field of view, e.g. 61.4 mm × 61.4 mm at a scale factor of 1:1 is provided by a 4096 × 4097 pixel 2 CCD-camera. The set up ensures great adaptivity to fuel cells of various sizes along with the best possible spatial resolution. Studies on the water transport in a DMFC and PEMFC are presented to demonstrate the capacity of the detector system.

We have simulated, built and tested a neutron solid state lens based on a modified bender model. The device is 140 mm long and has a focus at a distance of 31 mm behind the end of the lens. It is made of two stacks of 150 μm thick silicon wafers in an aluminum bender with a 20×30 mm 2 entrance window. The wafers are coated with m =2Ni–Ti supermirrors and the lens can thus accept the full divergence of a guide with the same wall coating. Measurements were performed with neutrons of wavelength 0.5 nm at the HZB. They showed in the focal line a FWHM of 2.4 mm and a maximum intensity gain of a factor 5.6 when compared to the intensity at the same position without the lens.

Differential phase contrast imaging resolves angular deviations of a beam due to phase shifts induced by a sample and thereby enables the visualisation and three-dimensional reconstruction of the refractive index distribution of a sample additional to the attenuation coefficient addressed by conventional radiography and tomography. Two instrumental techniques, namely double crystal diffractometers and a grating interferometer setup, are suitable to detect this kind of contrast. According to the high angular resolution of these methods they are suited to additionally detect dark field contrast, i.e. (ultra) small angle scattering contrast. Magnetic fields add to the refractive index for neutrons and consequently magnetic structures can in principle also be imaged by these methods. Relations between the methods will be discussed and an overview of current developments will be given.

Neutrons are highly sensitive to magnetic fields because of their intrinsic magnetic moment. At the same time, their zero net electrical charge allows them to penetrate thick layers of matter. In combination with standard radiographic and tomographic imaging techniques, these properties have been exploited to visualize magnetic fields in free space and within the bulk of solid, massive, opaque samples. In this paper, the basic principle of this new technique and its realization at the CONRAD instrument at the Helmholtz Centre Berlin (formerly Hahn-Meitner Institute Berlin) are explained. Two application examples will be given: the visualization of the magnetic field around a permanent magnet and the investigation of the displacement of the current density from the core of a conductor to the surface (the skin effect).

Water flow imaging may help to better understand various problems related to water stress of plants. It may help to fully understand the water relations of plants. The objective of this research was to estimate the velocity of water flow in plant samples. Cut roses (Rosa hybrida, var. ‘Milva’) were used as samples. Cold neutron radiography (CNR) was conducted at CONRAD, Helmholtz Center Berlin for Materials and Energy, Berlin, Germany. D2O and H2O were interchangeably injected into the water feeding system of the sample. After the uptake of D2O, the neutron transmission increased due to the smaller attenuation coefficient of D2O compared to H2O. Replacement of D2O in the rose peduncle was clearly observed. Three different optical flow algorithms, Block Matching, Horn–Schunck and Lucas–Kanade, were used to calculate the vector of D2O tracer flow. The quality of sequential images providing sufficient spatial and temporal resolution allowed to estimate flow vector.

Edge enhancement is the main effect measured by the so-called inline or propagation-based neutron phase contrast imaging method. The effect has originally been explained by diffraction, and high spatial coherence has been claimed to be a necessary precondition. However, edge enhancement has also been found in conventional imaging with high resolution. In such cases the effects can produce artefacts and hinder quantification. In this letter the edge effects at cylindrical shaped samples and long straight edges have been studied in detail. The enhancement can be explained by refraction and total reflection. Using high-resolution imaging, where spatial resolutions better than 50 μm could be achieved, refraction and total reflection peaks – similar to diffraction patterns – could be separated and distinguished.

In the past, neutron imaging investigations have been mostly performed in “integrating mode”, which averages over the full applied neutron energy spectrum. This article describes four different methods and devices of obtaining energy selectivity in the thermal to cold energy range, which allow a new approach in neutron imaging. Two principles have been used and tested: (a) selection of neutrons by suppression of contribution of other spectral parts; (b) using the flight-time information in distance from the source. For the (a) option, three different devices have been exploited practically. Information about material properties can be revealed that cannot be obtained in integrating mode. The energy-dependent transmission measurements make use of the Bragg edges in the total cross-sections of materials. Energy-selective radiography has vast potential for contrast variation, and for mapping structural properties such as crystallographic texture and residual strains with high spatial resolution. The obtained images highlight new opportunities in materials and engineering research, in comparison and complementary to what can be obtained by neutron scattering. There is likely to be an increasing need for implementing time-of-flight neutron imaging at present and future pulsed spallation sources, where the energy range can be selected almost without limitations. In this paper we attempt to give an overview over the current state of the art of energy-selective imaging and the experimental configurations required.

Conventional neutron imaging is based on the mapping of the attenuation function for a sample in a neutron beam. The intensity map obtained can be represented as an image with two main parameters: spatial resolution and contrast. The spatial resolution is influenced by the beam definition (collimation) and the detector system, whereas the contrast is governed by the interaction of the neutrons with matter, i.e. through absorption and scattering in the sample.

Improving the spatial resolution conditions in a neutron imaging experiment enables the detection of phase-based contrast in addition to attenuation contrast. Addressing not only the amplitude but also the phase of radiation in an imaging experiment allows for obtaining additional information about the sample. The so-called neutron phase contrast method improves imaging results mainly by edge enhancement which increases the visibility of sub-resolution structures and of low attenuation contrast materials. These effects have been found at high intensity synchrotron X-ray sources before and have been applied to neutron imaging recently. However, the excellent coherence conditions and spatial resolution of imaging instruments at state-of-the-art synchrotron sources can hardly be compared to neutron imaging. Nevertheless, edge enhancement has been found for increased resolution (coherence) conditions in neutron experiments as well. As for X-ray instruments the effects have been explained by diffraction, although typical interference fringes have never been recorded. In contrast this article will explain the effects measured with neutron radiation by refraction and total reflection. Both of these do not require high spatial coherence. Therefore improved resolution and not increased coherence will be considered as precondition to obtain the reported signals and to understand the results. Considerations concerning relaxed collimation requirements for improved detector resolutions will be presented as a consequence.

A neutron transport system for the planned imaging instrument ODIN at the future European Spallation Source (ESS) based on neutron optical components was designed and optimized. Different ways of prompt pulse suppression were studied. The spectral performance of the optimal neutron guide configuration is presented. In addition, the influence of the gaps in the guide system needed for the required chopper configuration was investigated. Given that the requirements for an imaging instrument located on a long guide system and hosting a complex chopper system are extremely demanding in terms of spectral and divergence needs, this study can be beneficial for a wide range of instruments in various ways.

Double-crystal diffractometers (DCD) are widely used for structural investigations at the limit between macroscopic and microscopic inner structures of sample materials. Operating in an ultra-small-angle scattering q -range between 10 −4 and 10 −1 nm −1 structures between 50 nm and nearly 100 μm can be resolved. Hence the DCD connects the resolvable ranges of small-angle neutron scattering (SANS) instruments and neutron tomography facilities. However, the DCD does not only link the resolvable size ranges but can also be operated to yield both, q -space information on microscopic structures combined with real space information in the range of macroscopic inner structures. This method was developed in recent years at the V12 DCD at HMI by introducing refraction and ultra-small-angle neutron scattering (USANS) contrast for tomography. The new V12 DCD set-up has now been optimized to exploit all the opportunities of USANS, refraction and USANS contrast tomography and conventional attenuation contrast tomography with an intense monochromatic neutron beam. The new contrast methods will be introduced as well as the final set-up of the V12 instrument. Additionally, several examples and results achieved by the new techniques and instrument will be given.

The lateral coherence properties of a neutron beam ( λ = 0.5248 nm ) in a double crystal diffractometer (DCD) were studied by means of single slit diffraction and by diffraction by different perfect Silicon phase gratings. Perfect agreements were found for the lateral coherence length measured with the slit and for the one determined by Silicon phase gratings, however, some peculiarities are still present.

Within the last decade neutron tomography and radiography significantly gained importance. Especially its application in non-destructive testing for industrial components can be underlined. A good example is the automotive and aviation industry, where a high contrast for the used lubricants and adhesive materials is required. In contrast to X-rays, neutrons are able to penetrate thick layers of metals and provide on the other hand a high sensitivity to hydrogen containing materials. In recent years, a large number of applications in other fields like biology, medicine, geology and especially archaeology have been reported. Here the potential of neutron tomography for investigations on archaeological samples shall be outlined and some recent examples will be presented.

Absorption is just one of a number of imaging signals used in neutron tomography. Within the last years, phase contrast, refraction and ultra small-angle scattering as imaging signals have been investigated as well as real-time radiography or energy-dispersive absorption. The use of cold neutrons (λ>0.3nm) implies for many neutron tomograms a better absorption contrast, larger refraction angles, larger small-angle scattering angles and better phase contrast. The reconstruction procedures for refraction and ultra small-angle scattering tomographies are different from other signals, however, they can be transformed to data sets and then be reconstructed with well-known programs. Examples will be given of all these techniques.

It has been shown in earlier works that smallest beam deviations (μrad) caused by refraction can be used to reconstruct the macroscopic inner structure of samples by the means of tomography. Hence, structures of low contrast materials, i.e. materials with low values or differences of attenuation coefficients, could be imaged by tomographic reconstruction although the conventional attenuation contrast method failed. Such tomographic scans have mainly been performed in a bent crystal-type double crystal diffractometer (DCD) using a one-dimensional position sensitive detector (PSD). This setup provided only q-resolution in the PSD, while the spatial resolution was achieved by scanning the sample through a slit collimated beam. The first practical application of this method shall be introduced here and advantages compared to the conventional method will be discussed. The measurement of two samples, a test with a dummy sample and a measurement of a sample requested by a company, are the examples to be reported.

We performed tomographic investigations of a sample with a special double crystal diffractometer (DCD) using only the refraction of a neutron beam as imaging signal. Up to now refraction contrast tomographies with DCDs have been performed with the standard detectors and linear position sensitive detectors (PSD). Especially the combination of a bent crystal type DCD with a PSD saved exposure time and increased the accuracy of the reconstructed image. However, the reconstructed objects had to be (high) slices of an object (having congruent cross sections in the height) due to the lack of any vertical resolution. Hence only two-dimensional slices of samples could be reconstructed and imaged. As the refraction effect is measured in a horizontal plane of scattering, other refraction angles out of that plane of scattering could be neglected. Therefore, a three-dimensional reconstruction of the sample volume becomes possible with a two-dimensional position sensitive detector. First results achieved by this set-up using the refraction contrast method will be given.

Using a double crystal diffractometer (DCD) for tomographic imaging introduces the possibility to use various signals for image contrast. In conventional neutron and X-ray radiography and tomography the contrast signal for imaging arises just from the attenuation in the sample. Due to recent developments in digital imaging tomography gained a lot of importance in medicine and non-destructive testing (NDT). But not all materials deliver an useful contrast concerning attenuation neither in the case of X-rays nor for neutrons. In a DCD attenuation but also other interactions between penetrating radiation and sample can be registered. Besides the common attenuation there are especially refraction and small-angle scattering effects. It will be shown at least for neutrons that from each of these signals recorded as tomographic projections in a DCD an image of the sample can be reconstructed by the means of common filtered back projection (FBP) algorithm. Additionally, all the signals can be registered in one measurement and can be used for independent reconstructions resulting in different images expressing different characteristics of the sample.

Slits and macroscopic objects such as edges give rise to refraction and diffraction. In this Letter we show the effect of Cd edges and slits if they are inserted between the monochromator and analyser in a double crystal diffractometer. Despite to the use of wavelengths of tens of nanometer and strong absorbing materials refraction is observed which contributes to enhanced wing intensity of the instrumental curve of the double crystal diffractometer.

Background The development of technological routes to convert lignocellulosic biomass to liquid fuels requires an in-depth understanding of the cell wall architecture of substrates. Essential pretreatment processes are conducted to reduce biomass recalcitrance and usually increase the reactive surface area. Quantitative three-dimensional information about both bulk and surface structural features of substrates needs to be obtained to expand our knowledge of substrates. In this work, phase-contrast tomography (PCT) was used to gather information about the structure of a model lignocellulosic biomass (piassava fibers). Results The three-dimensional cellular organization of piassava fibers was characterized by PCT using synchrotron radiation. This technique enabled important physical features that describe the substrate piassava fibers to be visualized and quantified. The external surface area of a fiber and internal surface area of the pores in a fiber could be determined separately. More than 96% of the overall surface area available to enzymes was in the bulk substrate. The pore surface area and length exhibited a positive linear relationship, where the slope of this relationship depended on the plant tissue. Conclusions We demonstrated that PCT is a powerful tool for the three-dimensional characterization of the cell wall features related to biomass recalcitrance. Original and relevant quantitative information about the structural features of the analyzed material were obtained. The data obtained by PCT can be used to improve processing routes to efficiently convert biomass feedstock into sugars.

We have developed the first tuneable channel cut crystal for ultra small angle neutron scattering and neutron optical experiments. The Darwin range of a perfect crystal can be reduced down to a fraction of its natural width. This “Darwin reduction” was realised without any change of the beam geometry which yields an intensity gain relative to conventional asymmetric Bragg diffraction. With such tuneable channel cut crystal peaks nearly δ -peaks can experimentally be realised.

Neutron imaging is a method for non-destructive investigations of objects in science and engineering. Different contrast mechanisms provide information about the interior structure of samples. High-resolution neutron tomography is used for the reconstruction of the three-dimensional matrix of attenuation coefficients in the sample. Energy-selective radiography performed around Bragg-cut-off wavelengths makes structure defects and textures visible. Imaging with polarized neutrons makes it possible to visualize magnetic fields in bulk samples. Examples of different experimental techniques will be presented and discussed.

Cold neutrons have a wavelength that is in the same range as the dhkl spaces for polycrystalline metal materials. Therefore imaging of polycrystalline materials with monochromatic cold neutrons provides a unique contrast due to coherent Bragg scattering. Here, we present investigations of metallic materials with energy-selective neutron radiography around the Bragg-edges for polycrystalline materials. Polychromatic and monochromatic radiographic measurements of welded composite materials are shown. The results give interesting insights into the manufacturing process.

Simultaneous use of neutron diffraction and attenuation based transmission Bragg edge imaging for strain measurements is demonstrated in this paper using the pulse neutron source at Los Alamos National Laboratory. Cylindrical samples made from ferritic steel have been subjected to in-situ elastic loading in tension and torsion. Lattice strains were investigated for both deformation modes by time-of-flight (TOF) neutron diffraction using two detector banks at 2θ of ±90°. At the same time, the transmitted portion of the neutron beam was recorded with the goal to analyze the position and shape of the Bragg edges, using a novel time/energy resolved Microchannel Plate (MCP) detector with pixel size of 55 µm and a 28x28 mm2 field of view. Lattice strains obtained using neutron diffraction indicate that the deformation path (tension versus torsion) has important effect on their evolution and related results are summarized.The emphasis of this paper is to explain the aspects of the experimental setup and data interpretation associated with neutron Bragg edge transmission technique for obtaining through-thickness averaged strain measurements. Implications of using transmission imaging based strain mapping for samples subjected to deformation under tensile loading (where stress at a given cross-section is constant) versus torsional loading (where stress varies linearly from center to outer radius) are discussed. In the case of samples subjected to tensile loading, analysis of the Bragg edge shifts provides the strain value in the direction of the transmitted beam. Thus, three strain components are measured simultaneously when performing Bragg edge imaging in addition to diffraction using two detector banks. For specimens subjected to pure shear by torsion, the Bragg edge transmission technique cannot readily provide quantitative strain information as the mid-point of the Bragg edge does not shift uniformly due to external loading, but results in a broadening of the Bragg edge. Such information can be used to describe the variation of strain distribution along the transmitted beam direction. Spatially resolved Bragg edge maps will be very helpful to detect d-spacing inhomogeneities within the illuminated volume, which may remain undetected when using diffraction only measurements.