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We describe in this paper the experimental procedure, the data treatment and the quantification of the black body correction: an experimental approach to compensate for scattering and systematic biases in quantitative neutron imaging based on experimental data. The correction algorithm is based on two steps; estimation of the scattering component a...
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... This resulted in one intensity value per virtual black body, which was subsequently used for the thin-plate spline interpolation to obtain the scattering images (I S n,BB and I S OB,BB ) (Carminati et al.,125 2019; Lombardo et al., 2025c). Due to significant amount of scattering from the water and ice, a beam hardening correction was applied to the scattering-corrected optical density using the polynomial expression (y = 0.99x + 0.03x 2 + 0.0009x 3 ) reported by Carminati et al. (2019) for the NEUTRA beamline, where x is the calculated optical density from Eq. 1 and y is the optical density after the beam-hardening correction. Finally, the optical density of the glass column walls (0.192 ± 0.009) was subtracted from the beam-hardening corrected optical density. ...
... The correction method was validated by measuring the linear attenuation coefficient of water and comparing it to the value of 3.6 cm -1 reported by Carminati et al. (2019). The linear attenuation coefficient is related to the optical density through ...
... The linear 135 attenuation coefficient of water was measured with an aluminum wedge with steps of different water thicknesses in the beam direction (path lengths) between 0.5 mm and 5 mm. Applied to the wedge, the correction method resulted in a linear attenuation coefficient for water of 3.60 ± 0.02 cm -1 (Fig. 3), which matches the value of 3.6 cm -1 reported by Carminati et al. (2019). ...
Liquid water flow in snow is important for snow hydrology, remote sensing, and avalanche formation. Water flow in snow is often dominated by capillary effects, which are responsible for the formation of capillary barriers, capillary flow paths, and capillary rise. Unfortunately, there is little quantitative data on the capillary forces of snow, particularly with respect to capillary rise dynamics. Here, we present the results of 4 capillary rise experiments using neutron radiography. The experiments were performed in 13 x 13 x 1 cm3 glass columns with sand-snow and sand-gravel-snow layering mimicking the capillary forces at the soil-snow interface. Images were taken at 10 s to 15 s intervals with a pixel size of 92 μm. The experiments provided quantitative results of high resolution liquid water profiles, wetting front progression, flow rates, and parameterization of snow hydraulic properties. The experiments showed that the snow properties influenced the capillary rise height while the hydraulic properties of the transitional layer below the snow influenced the flow rates. Flow rates in all three layers were significantly below the expected saturated hydraulic conductivity values.
... The scattering correction was performed using established black body methodology, 21,22 for which a set of 26 black-body sample projections evenly distributed over 360°(angular step of 14.4°) and 10 open beam black body images were acquired. ...
Hybrid implants consisting of a permanent Ti-based part combined with a degradable Mg part, are promising solutions to design superior implants by combining the advantages of both materials. In these implants Ti provides high strength while a degradable Mg part is used for temporary structural support, bone growth stimulation or drug delivery purpose. As Mg degrades hydrogen gas is released which can ingress into the Ti part, leading to changes in its properties. The profile of hydrogen distribution is a critical parameter for mechanical stability of Ti, especially in long-term applications. To investigate this in microscopic length scale, Ti6Al4V–Mg0.6Zn0.5Ca hybrid samples prepared using metal injection molding were subjected to saline degradation for a period of 0 to 120 hours. Neutron tomography, synchrotron X-ray tomography and diffraction, SEM and gas fusion technique were used to study the ingress of hydrogen in 3D after the degradation of MgZnCa. A uniform distribution of hydrogen was seen radially while the profile along height matched with macroscopic measurements. Synchrotron XRD confirmed that the room temperature diffusion of hydrogen led to lattice expansion of the BCC β-phase in Ti6Al4V, while no hydride phases were present.
... These tubes were subject to the methane pressure step, the diffusion of methane into the liquid was imaged. After applying filters and corrections 29,30 , the radiographs were reconstructed at the central plane of the sample via the onion-peeling algorithm 31 . The resulting tomographic reconstructions at the central plane of the sample (Fig. 1) are matrices of the overall linear attenuation coefficient (Σ) for the individual pixels. ...
Bulk properties of two-phase systems comprising methane and liquid p-xylene were derived experimentally using neutron imaging and theoretically predicted using molecular dynamics (MD). The measured and predicted methane diffusivity in the liquid, Henry’s law constant, apparent molar volume, and surface tension compared well within the experimentally studied conditions (273.15 to 303.15 K, ≤ 100 bar). Since MD is a physical model, extrapolations of the two-phase systems properties were performed for a broader temperature range (260 to 400 K, ≤ 100 bar). Moreover, the species diffusivities in single phases formed by infinitely diluted p-xylene in methane were predicted under conditions relevant to the methane liquefaction (90 to 290 K, 50 bar). The predicted p-xylene diffusivity in the supercritical methane was one order of magnitude higher than that calculated using Wilke–Chang and He–Yu correlations. This study provides novel experimental and MD-simulated characteristics for this industrially relevant system, for which intensive freeze-out formation from the supercritical methane is predicted.
... It is important to note that the presence of the BBs themselves influences the overall neutron flux reaching the scintillator. Therefore a, so called, dose operator D in accordance with practices for neutron-imaging quantification 66 was calculated in regions outside the orifice active region excluding BB locations, as annotated in the regions of interest of Fig. 10c The dose operator was calculated using the dark-current corrected stagnantflow images, where the averaged (within the ROI) intensity in the absence BBs was divided by the equivalent one for BBs present, as follows: The resulting map of correction values (Fig. 10d) results by multiplying the dose operator by the 2D matrix of interpolated scattering-contribution values and is applied on a per-pixel manner to raw images to account for scattering effects in the attenuation law of Eq. (4). It should be noted that the probability of a neutron scattering event is characterised by cross-sections, i.e., essentially probabilistic measures of the likelihood of a particular interaction (scattering or absorption) occurring when a neutron encounters a nucleus. ...
The current experimental investigation demonstrates the capability of neutron imaging to quantify cavitation, in terms of vapour content, within an orifice of an abruptly constricting geometry. The morphology of different cavitation regimes setting in was properly visualised owing to the high spatial resolution of 16 μm achieved, given the extensive field of view of 12.9 × 12.9 mm² offered by the imaging set-up. At a second step, the method was proven capable of highlighting subtle differences between fluids of different rheological properties. More specifically, a reference liquid was comparatively assessed against a counterpart additised with a Quaternary Ammonium Salt (QAS) agent, thus obtaining a viscoelastic behaviour. In accordance with previous studies, it was verified, yet in a quantifiable manner, that the presence of viscoelastic additives affects the overall cavitation topology by promoting the formation of more localised vortical cavities rather than cloud-like structures occupying a larger portion of the orifice core. To the authors’ best knowledge, the present work is the first to demonstrate that neutron imaging is suitable for quantifying in-nozzle cavitating flow at the micrometre level, consequently elucidating the distinct forms of vaporous structures that arise. The potential of incorporating neutron irradiation for the quantification of two-phase flows in metallic microfluidics devices has been established.
... This normalization is, however, biased due to the contribution from neutrons, which were scattered from the sample and background. Two reference images (with and without the sample) were obtained with a black body grid installed to measure the scattering contribution [30]. This involved the use of 5-mm thick aluminum frame including a 10 × 10 grid of Ø0.5 mm cylindrical inserts (black bodies) made of 10 B 4 C. ...
This study presents a preliminary examination of the effects of environment changes post-excavation on heavily corroded archaeological Roman iron nails using neutron tomography and image registration techniques. Roman nails were exposed to either a high relative humidity environment, or fast thermal drying as primary experiments to show the power of this imaging technique to monitor and quantify the structural changes of corroded metal artifacts. This research employed a series of pre- and post-treatment tomography acquisitions (time-series) complemented by advanced image registration methods. Based on mutual information (MI) metrics, we performed rigid body and affine image registrations to meticulously account for sample repositioning challenges and variations in imaging parameters. Using non-affine local registration results, in a second step, we detected localized expansion and shrinkage in the samples attributable to imposed environmental changes. Specifically, we observed local shrinkage on the nail that was dried, mostly in their Transformed Medium (TM), the outer layer where corrosion products are cementing soil and sand particles. Conversely, the sample subjected to high relative humidity environment exhibited localized expansion, with varying degrees of change across different regions. This work highlights the efficacy of our registration techniques in accommodating manual removal or loss of extraneous material (loosely adhering soil and TM layers around the nails) post-initial tomography, successfully capturing local structural changes with high precision. Using differential analysis on the accurately registered samples we could also detect and volumetrically quantify the variation in moisture and detect changes in active corrosion sites (ACS) in the sample. These preliminary experiments allowed us to advance and optimize the application of a neutron tomography and image registration workflow for future, more advanced experiments such as humidity fluctuations, corrosion removal through micro-blasting, dechlorination and other stabilization treatments.
... More recently, researchers from the Paul Scherrer Institute introduced a method to correct for systematic biases reported in Boillat et al [32] and Carminati et al [33]. The method relies on the use of an ordered array of black bodies (BBs) i.e. objects of known geometry with very high neutron absorption positioned before the sample with respect to the neutron beam. ...
... The same methodology can be extended to tomography where each angular projection is corrected in the same manner, prior to the reconstruction of the 3D attention fields. The method was shown to be highly effective in eliminating the artefacts caused by scattering [32][33][34]. Wissink et al [35] further improved the performance of this method in removing scattering artefacts by presenting a new method for the fabrication of the BB grids with an optimized design tailored to the particular experimental setup. ...
... Its presence can result in a reduction of the spurious scattering contributions on the sample (before correction). Carminati et al [33] introduced a coefficient denoted as τ BB that accounts for the reduction in the transmission at the grid crossings, assuming that the reduction of scattering can be described as homogeneous. This scalar coefficient can be approximated by the mean transmission of the grid. ...
Neutron imaging has gained increasing attention in recent years. A notable domain is the in-situ study of flow and concentration of hydrogen-rich materials. This demands precise quantification of the evolving concentrations. Several implementations deviate from the ideal conditions that allow the direct applicability of the Beer–Lambert law to assess this concentration. The objective of this work is to address these deviations by applying both calibration and correction procedures to ensure and validate accurate quantitative measurements during 2D and 3D neutron imaging conducted at the cold neutron source at the NeXT instrument of the Institute Laue–Langevin, Grenoble, France. Linear attenuation coefficients and non-linear correlations have been proposed to measure the water concentration based on the sample-to-detector distance. Furthermore, the effectiveness of the black body grid correction method, introduced by Boillat et al (2018 Opt. Express 26 15769), is evaluated which accounts for spurious deviations arising from the scattering of neutrons from the sample and the surrounding environment. The applicability of the Beer–Lambert law without any data correction is found to be reasonable within limited equivalent thickness (e.g. below 4 mm of water) beyond which the correction algorithm proves highly effective in eliminating spurious effects. Notably, this correction method maintains its effectiveness even with transmissions below 1%. We examine here the impact of grid location and resolution with respect to sample heterogeneity.
... More information about the FISH neutron imaging station can be found elsewhere [33]. The scattering corrections have been performed using an established black bodies methodology [34,35]. ...
The steel–concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete’s opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to elucidate the mechanism of steel corrosion in concrete. The study demonstrates that the segmentation of the specimen components of relevance—steel, cementitious matrix, aggregates, voids, corrosion products—obtained through bimodal X-ray and neutron imaging is more reliable than that based on the results of each of the two techniques separately. Further, we suggest the combination of tomographic in-situ imaging with ex-situ SEM analysis of targeted sections, selected based on the segmented tomograms. These in-situ and ex-situ characterization techniques were applied to study localized corrosion in a very early stage under laboratory chloride-exposure conditions, using reinforced concrete cores retrieved from a concrete bridge. Several interesting observations were made. First, the acquired images revealed the formation of several corrosion sites close to each other. Second, the morphology of the corrosion pits was relatively shallow. Finally, only about half of the total 31 corrosion initiation spots were in close proximity to interfacial macroscopic air voids, and > 90% of the more than 160 interfacial macroscopic air voids were free from corrosion. The findings have implications for the mechanistic understanding of corrosion of steel in concrete and suggest that multimodal in-situ imaging is a valuable technique for further related studies.
Supplementary Information
The online version contains supplementary material available at 10.1617/s11527-024-02337-7.
... For this research, the images were processed using Kiptool, a multiplatform general purpose software to process 2D and 3D imaging data [31]. The importance of appropriate data correction for useful results (namely removing sample and set-up scattering by means of black bodies) has been highlighted in previous research [32,33] and was applied here. The steps for image acquisition were as follows: open beam (10 images), dark current (10 images) and black body images (10 images) were obtained for each series to perform the corresponding corrections (neutron beam intensity, camera noise, background scattering). ...
During capillary imbibition, there are changes in the pore structure that reduce the water ingress rate, leading to anomalous behaviour. However, the relation of those deformations with the C-S-H content is still unclear. We performed simultaneous measurements of external deformations and water ingress through neutron radiography. Cement pastes of water/cement of 0.4 and 0.6, using both Portland and white cement were tested after 1 year curing. Porosity and calcium silicate hydrate (C-S-H) content of the pastes were determined. Strain gauges were attached perpendicular and parallel to the water flow. Results indicate that the degree of internal restriction of the mix influences the shape of the water profile and that C-S-H deformations affect internal changes more than external. Water ingress visualisation indicated the lack of a sharp front during imbibition and the saturation degree variation at the position of the strain gauges. We propose a model to address the dynamic porosity.
... A grid of perfect neutron absorbers, black-bodies, were used to facilitate the scattering correction described below. Here, we used 10 B 4 C cylinders with a diameter of 2.5 mm and a thickness in the beam direction of 3 mm which were mounted in an aluminum grid at 25 mm center-to-center spacing (Carminati and others, 2019). The black-body grid is placed in front of the chamber. ...
... The open-beam image (here, taken with the black-body grid) accounts for non-sample attenuation (here, the empty climatic chamber and black-body grid). The scattering contribution is calculated with the measured intensity behind a grid of perfectly absorbing black-bodies (described in detail below) (Carminati and others, 2019). Finally, dosis terms are used to account for fluctuations in the incoming neutron beam intensity. ...
Liquid water at the ground–snow interface is thought to play a crucial role in the release of glide-snow avalanches, which can be massive and threaten infrastructure in alpine regions. Several mechanisms have been postulated to explain the formation of this interfacial water. However, these mechanisms remain poorly understood, in part because suitable measurement techniques are lacking. Here, we demonstrate the use of neutron radiography for imaging water transport in soil–snow systems. Columns of sand, gravel and snow were used to simulate the capillary forces of the soil–vegetation–snow layering found in nature. The columns were connected to a water reservoir to maintain a constant-pressure boundary condition and placed in a climatic chamber within the neutron beam. We show that neutron radiography is capable of measuring changes in the optical density distribution (related to liquid water content) within all three layers of the model system. Results suggest that a porous interface between the sand and snow may induce the formation of a water layer in the basal snowpack. Improved understanding of the water transport in soil–snow systems should lead to better prediction of glide-snow avalanche release and could also benefit other fields such as snow hydrology.
... 10 B 4 C is almost completely opaque to a neutron beam. Thus, any neutron beam's transmitted intensity recorded on the detector plane at the line projection position of such black bodies is only due to neutron scattering events and can be used for scattering evaluation and correction of the respectively induced bias in the acquired neutron radiographs [58]. ...
... Additionally, the dark-current radiograph, acquired with no neutron beam, is commonly subtracted from I comp (x, y) and I 0 (x, y) in order to remove the pixel-wise background noise of the CCD camera. Various methods were also proposed in the literature to estimate the background and sample scattering, e.g., the Quantitative Neutron Imaging (QNI) approach based upon estimations of scattering point spread functions (PScF) [58,63]. In this study, a fully experimental method for correcting for both the background and the sample scattering [58,64] was used. ...
... Various methods were also proposed in the literature to estimate the background and sample scattering, e.g., the Quantitative Neutron Imaging (QNI) approach based upon estimations of scattering point spread functions (PScF) [58,63]. In this study, a fully experimental method for correcting for both the background and the sample scattering [58,64] was used. According to this method, BB radiographs collected with and without specimens were needed. ...
The drying process has a prominent impact on the volume changes, crack propagation and durability of concrete structures. This study is to quantify the moisture distribution in real-time drying cement mortars. Mortar prisms with different water-to-cement ratios (w/c) and superabsorbent polymers (SAP) amounts were cut into slices and prepared with distinct lengths of cut notches. They were subjected to accelerated drying during neutron radiography measurements. In mortars with higher w/c, the coarser pores accelerate water transport and lead to more rapid drying. The large voids and the SAP in the bulk of the specimens are emptied well before the exposed surface starts to dry out. The presence of notches enhances drying. However, the moisture loss through the notches is less efficient than through the external surfaces. The competition between evaporation from the surfaces and moisture transport within the material, in both liquid and gas forms, governs the moisture distribution evolution.
