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To investigate the feasibility of using neutron tomography to gain new knowledge of human articular cartilage degeneration in osteoarthritis (OA). Different sample preparation techniques were evaluated to identify maximum intra-tissue contrast. Human articular cartilage samples from 14 deceased donors (18–75 years, 9 males, 5 females) and 4 patients undergoing total knee replacement due to known OA (all female, 61–75 years) were prepared using different techniques: control in saline, treated with heavy water saline, fixed and treated in heavy water saline, and fixed and dehydrated with ethanol. Neutron tomographic imaging (isotropic voxel sizes from 7.5 to 13.5 µm) was performed at two large scale facilities. The 3D images were evaluated for gradients in hydrogen attenuation as well as compared to images from absorption X-ray tomography, magnetic resonance imaging, and histology. Cartilage was distinguishable from background and other tissues in neutron tomographs. Intra-tissue contrast was highest in heavy water-treated samples, which showed a clear gradient from the cartilage surface to the bone interface. Increased neutron flux or exposure time improved image quality but did not affect the ability to detect gradients. Samples from older donors showed high variation in gradient profile, especially from donors with known OA. Neutron tomography is a viable technique for specialized studies of cartilage, particularly for quantifying properties relating to the hydrogen density of the tissue matrix or water movement in the tissue. [ABSTRACT FROM AUTHOR]

The use of a phase‐retrieval technique for propagation‐based phase‐contrast neutron imaging with a polychromatic beam is demonstrated. This enables imaging of samples with low absorption contrast and/or improving the signal‐to‐noise ratio to facilitate e.g. time‐resolved measurements. A metal sample, designed to be close to a phase pure object, and a bone sample with canals partially filled with D2O were used for demonstrating the technique. These samples were imaged with a polychromatic neutron beam followed by phase retrieval. For both samples the signal‐to‐noise ratios were significantly improved and, in the case of the bone sample, the phase retrieval allowed for separation of bone and D2O, which is important for example for in situ flow experiments. The use of deuteration contrast avoids the use of chemical contrast enhancement and makes neutron imaging an interesting complementary method to X‐ray imaging of bone. [ABSTRACT FROM AUTHOR]

Freeze-drying frozen maltodextrin solutions with solid contents of 5% and 30% (w/w) was experimentally investigated using neutron imaging at PSI Villigen/Switzerland. Different solid contents, as well as annealing at −5 °C for 11 h, were used to modify the porous structure of the samples, which was quantified using X-ray computed tomography. Annealing of the 5% (w/w) sample, with a pore size distribution (PSD) of 23.7 ± 11.1 µm, yielded a very open pore space with high porosity (ε = 0.96) and a PSD of 33.0 ± 27.0 µm. In contrast, the higher solid content resulted in small, lamellar, narrow pores with high anisotropy and a porosity of ε = 0.65, as well as a PSD of 13.5 ± 4 µm. In operando neutron imaging was used to show the impact of the structure of frozen maltodextrin on the overall drying kinetics and shape of the sublimation front during freeze-drying. For this purpose, a freeze-drying stage was employed, which allowed a novel approach to time- and space-resolved monitoring of the ice phase. The sublimation front propagation was quantitatively analyzed based on ice saturation profiles and sublimation rates. The dependence of drying velocity on structure is nicely demonstrated by the data. In addition, it is shown that the sublimation front widened during freeze-drying, resulting in either rather concave or convex shape depending on morphological parameters. [ABSTRACT FROM AUTHOR]

4D wavelength‐resolved neutron tomography of a reference sample made of several polycrystalline materials, namely nickel, iron, titanium, lead, copper and aluminium, is presented. Data were acquired using the time‐of‐flight transmission imaging method at the IMAT beamline at the ISIS pulsed neutron source. Wavelength‐dispersive tomography reconstruction was computed using filtered back projection, allowing wavelength‐resolved total‐cross‐section retrieval for each voxel in the reconstructed volume of the sample. The need for background correction to enable quantitative results and analysis is discussed, and the achieved 3D spatial resolution with respect to the obtained Bragg‐edge pattern quality is investigated. [ABSTRACT FROM AUTHOR]

European beech ( Fagus sylvatica L.) and Norway spruce [ Picea abies (L.) Karst.] have been thermally modified in a combined air-steam atmosphere between 70°C and 150°C and pressures up to 4 bar, and the changes of dimensions and moisture contents (MC) of the samples were studied in-situ by means of neutron imaging (NI). This non-invasive testing method offers unique opportunities. NI is highly sensitive for hydrogen and thus well suited for monitoring the MC changes, although some metals (e.g., Al), indispensable for sample environments under high temperature and pressure, are practically transparent to neutrons. The results show that the modification induced changes of MC and dimensions both in radial and tangential direction can well be determined by NI. Dimensional changes from water saturation to oven-dry state, the sorption isotherms, and the differential swelling were observed. Additionally, the sorption behaviour at 20°C was investigated after thermal modification and colour measurements were carried out before and after the thermal treatment. [ABSTRACT FROM AUTHOR]

Abstract: In the framework of the post-test examinations of the large-scale LOCA simulation tests at the fuel rod bundle scale, the hydrogen distributions in specimens prepared from the QUENCH-L0 and -L1 tests were studied by means of neutron radiography and tomography. In order to determine quantitative hydrogen concentrations, both, neutron radiography and tomography were calibrated using cladding tube segments with known hydrogen concentrations. The linear dependence of the total macroscopic neutron cross section with the H/Zr atomic ratio was determined for both methods. The hydrogen distributions in samples prepared from the two tests differ significantly as a first glance to the results obtained for the QUENCH-L1 shows. Whereas clearly visible hydrogen bands were found in samples of the QUENCH-L0 test with a time between burst and quenching of more than 70 s; in some specimens prepared from the QUENCH-L1 test only blurred bands could be detected. The reasons for these different behaviors can be the different times between reaching the temperature maxima and the quenching, as well as bending of the QUENCH-L1 bundle. In the QUENCH-L0 test the bundle was quenched immediately after reaching the maximal temperature. In QUENCH-L1 the hydrogen had about 130 s to diffuse and reach more homogeneous distributions without clear contrasts between the hydrogen bands and the neighboring regions in the neutron images. [Copyright &y& Elsevier]

Abstract: Neutron imaging as a technique for non-destructive testing has its application range where the more common X-ray methods will come to their limits: transmission through thick layers of heavy metals, detection of small amounts of hydrogenous materials and some other light elements like Boron or Lithium. There are at least three approaches for the further methodical improvements in respect to industrial applications: better spatial resolution, adequate time resolution and the optimization of the contrast between components. Dedicated examples for the methodical improvements are shown. [Copyright &y& Elsevier]

Abstract: A new tool for computed tomography reconstruction is presented. The tool was developed to support the needs of users at neutron imaging beamlines and as a platform for algorithm development. It includes methods to handle large samples and artifact removal. The design is modular and allows tests of new concepts for preprocessing and back-projection. The reconstructor is tuned to provide the results fast even on a laptop computer. The reconstructor also has a graphical user interface which can be operated by new users after a short instruction. [Copyright &y& Elsevier]

Cork is the natural material stripped from the outer bark of cork oak. It is still the most used stopper to seal wine bottles and to preserve wine during storage. Cork stoppers are sorted in different classes according to apparent defects, named lenticels, which can be related to the cork macroporosity. The more lenticels there are, the worst cork quality is. The present work aims at investigating defects analysis of cork stoppers from two classes by comparing images recorded by digital photography and neutron imaging. Surface analysis of defects obtained from photography leads to more surface defects in class 4 (6.7%) than in class 0 (4.1%). Neutron radiography and tomography are powerful methods that really show the defects inside the material. From neutron radiography and tomography, class 4 contains 7.5% of volume defects and class 0 5.9%. Moreover, tomography also allows observing defects distribution along the whole stopper and possible interconnectivity. [ABSTRACT FROM AUTHOR]

Abstract: Conversion of thermal and cold neutrons into a strong ∼1ns electron pulse with an absolute neutron detection efficiency as high as 50–70% makes detectors with 10B-doped Microchannel Plates (MCPs) very attractive for neutron radiography and microtomography applications. The subsequent signal amplification preserves the location of the event within the MCP pore (typically 6–10μm in diameter), providing the possibility to perform neutron counting with high spatial resolution. Different event centroiding techniques of the charge landing on a patterned anode enable accurate reconstruction of the neutron position, provided the charge footprints do not overlap within the time required for event processing. The new fast 2×2 Timepix readout with >1.2kHz frame rates provides the unique possibility to detect neutrons with sub-15μm resolution at several MHz/cm2 counting rates. The results of high resolution neutron radiography experiments presented in this paper, demonstrate the sub-15μm resolution capability of our detection system. The high degree of collimation and cold spectrum of ICON and BOA beamlines combined with the high spatial resolution and detection efficiency of MCP-Timepix detectors are crucial for high contrast neutron radiography and microtomography with high spatial resolution. The next generation of Timepix electronics with sparsified readout should enable counting rates in excess of 107 n/cm2/s taking full advantage of high beam intensity of present brightest neutron imaging facilities. [Copyright &y& Elsevier]

• Enhanced absorption through concentration-based convection. • Neutron imaging of water vapor absorption on aqueous sodium hydroxide. • Increased performance of heat and mass exchanger for sorption storage heat pump. Heat release from absorption storage heat pump by means of absorption of water vapor into aqueous sodium hydroxide is limited by uptake kinetics affecting temperature gain, as well as power- and energy density of the method. Earlier studies pinpoint that natural diffusion alone is not sufficient to reach higher uptake rate, and that the surface to bulk exchange has to be enforced. In this paper, different technical solutions to this problem for the heat storage application are introduced and studied by neutron imaging, enabling visual observation of water vapor uptake and diffusion. The experiments brought to the fore that the buoyancy changes associated with water uptake may be utilized to markedly enhance kinetics. This concept was applied on a vertically installed spiral finned tube operating as heat and mass exchanger for the absorption storage heat pump, also referred to as sorption heat storage. By flooding the space between the spiral fin with absorbent, water absorption into the vertical surface leads to a buoyancy driven movement of the liquid, supplying unspent aqueous NaOH to the vertical surface and exchanging it with the diluted liquid. This is found to increase the rate of absorption markedly. Under realistic heat storage specific operating conditions, a temperature gain of 12.5 K, an active area specific power of 1.28 kW/m2 and an energy density of 243 kWh/m3 in respect to the volume of charged absorbent (greatest volume) is reached. It is proposed that carful design of the spiral finned tube to enhance buoyancy movement will further improve overall sorption heat storage performance. [ABSTRACT FROM AUTHOR]

Early-age drying (immediately after casting) of mortars and the corresponding plastic shrinkage were studied using bimodal neutron/X-ray computed tomography. This novel, correlative 3D imaging mode enabled studying simultaneously and without any source of spurious perturbation the water migration and loss processes together with the corresponding deformations due to plastic shrinkage. Bimodal imaging opens up new possibilities for studying dynamic processes of coupled water transport and deformations in porous solids. The measurements were carried out on model systems (cylindrical mortar specimens with height of 19 mm). The study focused on the effect of a paraffin-based curing compound. Our results confirm that when the curing compound was applied directly onto the drying surface in a sufficient amount, both the evaporation rate and the rate of vertical displacement (settlement) were substantially reduced. The results shed a new light on the mechanisms of plastic shrinkage and the action of curing compounds. [ABSTRACT FROM AUTHOR]