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An elliptic focusing neutron guide was combined with a cold neutron imaging instrument to produce a cone-beam, whose parameters were then characterized both at the focal point and at the detector position. This point source geometry provides improved experimental conditions for tomographic applications, providing a larger beam cross-section and enabling geometric magnification. The experimental data were compared with Monte Carlo simulations and both experiments and simulations demonstrate superior spectral and geometric homogeneity of the cone-beam setup compared to the conventional pinhole geometry. [ABSTRACT FROM AUTHOR]

Abstract: 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 Fe65.7Co18Si0.8B15.5 foil with a thickness of 21–22μm and a saturation magnetization of 1.7T, and trapped magnetic flux in a superconducting lead cylinder. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: The neutron tomography instrument CONRAD has been in operation since 2005 at the Hahn-Meitner research reactor at Helmholtz-Zentrum Berlin (HZB). Over the last 5 years, significant developmental work has been performed to expand the radiographic and tomographic capabilities of the beamline . New techniques have been implemented, including imaging with polarized neutrons , Bragg-edge mapping , high-resolution neutron imaging and grating interferometry . These methods have been provided to the user community as tools to help address scientific problems over a broad range of topics such as superconductivity, materials research, life sciences , cultural heritage and paleontology . Industrial applications including fuel cell research have also been improved through these new developments. Descriptions and parameters of the developed options will be presented, along with prominent examples. [Copyright &y& Elsevier]

Abstract: The X-ray photon counting hybrid pixel camera XPAD3-S is a promising detector for small animal X-ray radiography and tomography. The increasing interest in neutron imaging as a complementary approach to X-ray imaging motivates the study of the potentialities of this device for neutrons. To investigate this issue, we have studied the response of XPAD3-S to alpha particles and cold neutrons. The neutron detection was obtained with passive converters placed in front of the sensor. This choice permits to easily assemble 2D neutron sensitive imagers without size constraints; it penalizes however the detector efficiency with respect to other solutions. In this paper, we first analyze the detector response to alpha particles under several conditions, then we investigate its imaging performances and its detection efficiency for cold neutrons. Finally, we present the first XPAD3-S neutron tomography. Most of the results are validated by Monte Carlo simulations that will also permit to extrapolate the detector response to thermal neutrons. [Copyright &y& Elsevier]

Abstract: While polarized neutrons have long proved to be an outstanding tool for the investigation of magnetic structures by scattering, we report on their potential for real space investigations of magnetic fields on a macroscopic scale by neutron imaging. Due to the ability of neutrons to penetrate thick layers of matter and their high sensitivity to magnetic fields owed to their magnetic moment, neutron imaging enables the investigation of magnetic fields even in bulk samples of condensed matter. We demonstrate how neutrons provide images of magnetic fields trapped in or expelled by superconductors or even reveal the path of electric currents due to the corresponding magnetic fields. [Copyright &y& Elsevier]

The phase-contrast imaging is based not only on the absorption contrast like in the conventional radiography but also on the contributions of the phase shifts induced by the propagation of a coherent radiation through the investigated sample. The strong phase changes on the borders between two media can be observed as sharp intensity variations on the radiography image. So the phase-contrast method is an edge-enhancement method which allows to visualize very fine structures where the conventional radiography provides unsatisfactory results.For the aims of the phase-contrast imaging a radiation with a high spatial but not necessarily chromatic coherence is required. In this way phase-contrast radiography experiments with a polychromatic thermal neutron beam possessing a high spatial transversal coherence can be performed. The reported results show that the developed phase-contrast neutron radiography can be used as a standard non-destructive investigation method. [Copyright &y& Elsevier]

Abstract: Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D2O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2ppm SO2 in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO2 was applied for 1h. During the experiment, CNR and CF imaging were conduced. H2O and D2O in the plant container were exchanged every 30min to observe water uptake. D2O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D2O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO2 as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency (F v/F m), a sensitive indicator of the efficacy and the integrity of plants’ photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants. [Copyright &y& Elsevier]

The paper describes how hydrogenous materials can be investigated with state-of-the-art neutron radiography detection methods. The methodical problems for a precise quantification and steps towards their solution are demonstrated. Based on several practical examples, the diversity of problems to be solved by neutron imaging is illustrated. [Copyright &y& Elsevier]

Abstract: We report an investigation of the phase transitions between water and ice using neutron imaging as a research tool. Because of the high scattering cross section of hydrogen for slow neutrons, very small amounts of water can easily be quantified by this technique. However, it is not easy to determine the aggregate state (liquid or solid) if the sample does not have a well defined size, as might happen in the case of water produced in PEM fuel cells. It is important to be able to judge the state of the water (or ice), particularly when it is not easily accessible or hidden by the surrounding structure. The neutron interaction properties of the two aggregates (water and ice) were investigated in dynamic series, in which light water and heavy water were frozen under controlled conditions; transmission images were taken continuously during the phase transition. In addition to the expected density reduction of the ice, some other features were also observed in the images, causing the derived neutron transmission data to differ from the tabulated nuclear data. Energy-selective experiments with thermally stabilized water (+10°C) and ice (−10°C) showed different interaction behaviors for the two aggregates in the neutron wavelength range of 2–6Å. We found clear differences in the absolute values of the attenuation cross-sections and the slopes of their energy dependencies. This result might be used in the future as a criterion to distinguish between the aggregate states in arbitrary water or ice assemblies. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]