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362 results on '"Kaestner, Anders"'

2. Polychromatic neutron phase contrast imaging of weakly absorbing samples enabled by phase retrieval

Author

Østergaard, Maja, Naver, Estrid Buhl, Kaestner, Anders, Willendrup, Peter K., Brüel, Annemarie, Sørensen, Henning Osholm, Thomsen, Jesper Skovhus, Schmidt, Søren, Poulsen, Henning Friis, Kuhn, Luise Theil, and Birkedal, Henrik

Subjects
Physics - Medical Physics
Abstract

We demonstrate the use of a phase retrieval technique for propagation-based phase contrast neutron imaging with a polychromatic beam. This enables imaging 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 pure phase 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 ratio were significantly improved and in 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.

Published
2022
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4. Resolving gas bubbles ascending in liquid metal from low-SNR neutron radiography images

Author

Birjukovs, Mihails, Trtik, Pavel, Kaestner, Anders, Hovind, Jan, Klevs, Martins, Gawryluk, Dariusz Jakub, Thomsen, Knud, and Jakovics, Andris

Subjects
Physics - Fluid Dynamics, Computer Science - Computer Vision and Pattern Recognition
Abstract

We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented - stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions similar to the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our previously developed methods. Significant improvements are observed as well as the capacity to reliably extract physically meaningful information from measurements performed under highly adverse imaging conditions. The showcased image processing solution and separate elements thereof are readily extendable beyond the present application, and have been made open-source.

Published
2021
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14. Statistical Uncertainty in Quantitative Neutron Radiography

Author

Piegsa, Florian M., Kaestner, Anders P., Antognini, Aldo, Eggenberger, Andreas, Kirch, Klaus, and Wichmann, Gunther

Subjects
Physics - Data Analysis, Statistics and Probability, Physics - Instrumentation and Detectors
Abstract

We demonstrate a novel procedure to calibrate neutron detection systems commonly used in standard neutron radiography. This calibration allows determining the uncertainties due to Poisson-like neutron counting statistics for each individual pixel of a radiographic image. The obtained statistical errors are necessary in order to perform a correct quantitative analysis. This fast and convenient method is applied to data measured at the cold neutron radiography facility ICON at the Paul Scherrer Institute. Moreover, from the results the effective neutron flux at the beam line is determined.

Published
2016
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16. 4D Neutron Imaging of Solute Transport and Fluid Flow in Sandstone Before and After Mineral Precipitation

Author

Shafabakhsh, Paiman (author), Cordonnier, Benoît (author), Pluymakers, Anne (author), Le Borgne, Tanguy (author), Mathiesen, Joachim (author), Linga, Gaute (author), Hu, Yi (author), Kaestner, Anders (author), Renard, François (author), Shafabakhsh, Paiman (author), Cordonnier, Benoît (author), Pluymakers, Anne (author), Le Borgne, Tanguy (author), Mathiesen, Joachim (author), Linga, Gaute (author), Hu, Yi (author), Kaestner, Anders (author), and Renard, François (author)

Abstract

In many geological systems, the porosity of rock or soil may evolve during mineral precipitation, a process that controls fluid transport properties. Here, we investigate the use of 4D neutron imaging to image flow and transport in Bentheim sandstone core samples before and after in-situ calcium carbonate precipitation. First, we demonstrate the applicability of neutron imaging to quantify the solute dispersion along the interface between heavy water and a cadmium aqueous solution. Then, we monitor the flow of heavy water within two Bentheim sandstone core samples before and after a step of in-situ mineral precipitation. The precipitation of calcium carbonate is induced by reactive mixing of two solutions containing CaCl2 and Na2CO3, either by injecting these two fluids one after each other (sequential experiment) or by injecting them in parallel (co-flow experiment). We use the contrast in neutron attenuation from time-resolved tomograms to derive three-dimensional fluid velocity field by using an inversion technique based on the advection-dispersion equation. Results show mineral precipitation induces a wider distribution of local flow velocities and leads to alterations in the main flow pathways. The flow distribution appears to be independent of the initial distribution in the sequential experiment, while in the co-flow experiment, we observed that higher initial local fluid velocities tended to increase slightly following precipitation. The outcome of this study contributes to progressing the knowledge in the domain of reactive solute and contaminant transport in the subsurface using the promising technique of neutron imaging., Applied Geophysics and Petrophysics

Published
2024
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19. Visualizing the morphology of vortex lattice domains in a bulk type-II superconductor

Author

Gruenzweig, Christian, Muehlbauer, Sebastian, Schulz, Michael, Gruenzweig, Matthias, Kaestner, Anders, Kohlbrecher, Joachim, Mikheenko, Pavlo, Reimann, Tommy, Keiderling, Uwe, and Boeni, Peter

Subjects
Condensed Matter - Superconductivity
Abstract

Analogous to the various states of condensed matter exhibiting crystalline, amorphous, liquid and spatially inhomogeneous phases, such structures are likewise observed in superconducting vortex matter., Comment: Paper will be newly submitted in another form

Published
2013

20. The FALCON double-detector Laue diffractometer add-on for grain mapping at POLDI

Author

Samothrakitis, Stavros, primary, Larsen, Camilla Buhl, additional, Kaestner, Anders, additional, Polatidis, Efthymios, additional, Čapek, Jan, additional, Hovind, Jan, additional, Fazan, Andrin, additional, Allibon, John, additional, Busi, Matteo, additional, Schmidt, Søren, additional, Kopeček, Jaromír, additional, and Strobl, Markus, additional

Published
2023
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25. Implementation of Dynamic Neutron Radiography and Integrated X-Ray and Neutron Tomography in Porous Carbonate Reservoir Rocks

Author

Miller Zambrano, Fareeha Hameed, Kaestner Anders, Lucia Mancini, and Emanuele Tondi

Subjects
neutron radiography, neutron tomography, X-ray microtomography, fluid flow, porous media, grainstones, Science
Abstract

The textural and geometrical properties of the pore networks (i.e., such as pore size distribution, pore shape, connectivity, and tortuosity) provides a primary control on the fluid storage and migration of geofluids within porous carbonate reservoirs. These properties are highly variable because of primary depositional conditions, diagenetic processes and deformation. This issue represents an important challenge for the characterization and exploitation plan in this type of reservoirs. In this study, the complementary properties of neutrons and X-ray experiments are carried out to better understand the effects of pore network properties on the hydraulic behavior of porous carbonates. Neutrons have unique properties and are particularly suitable for this study due to the sensitivity of neutrons to hydrogen-based fluids. The used methodology combines dynamic neutron radiography (NR), integrated X-ray and neutron tomography (XCT, NCT), and computational fluid dynamics simulations (lattice-Boltzmann method) of porous carbonate reservoir analogs from central and southern Italy. Dynamic 2D NR images provide information regarding the fluid transport and the wetting front dynamics related to the effect of heterogeneities (e.g., fractures and deformation bands) at the microscale. The combination of NCT (dry and wet samples) and XCT (dry), generates more information regarding the effective pore space contribution to fluid flow. The fluid flow simulations generate information about the connected pore network and the permeability evaluated rock sample at saturated condition.

Published
2019
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32. Polychromatic neutron phase-contrast imaging of weakly absorbing samples enabled by phase retrieval

Author

Østergaard, Maja, primary, Naver, Estrid Buhl, additional, Kaestner, Anders, additional, Willendrup, Peter K., additional, Brüel, Annemarie, additional, Sørensen, Henning Osholm, additional, Thomsen, Jesper Skovhus, additional, Schmidt, Søren, additional, Poulsen, Henning Friis, additional, Theil Kuhn, Luise, additional, and Birkedal, Henrik, additional

Published
2023
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33. Polychromatic neutron phase-contrast imaging of weakly absorbing samples enabled by phase retrieval

Author

Østergaard, Maja, Naver, Estrid Buhl, Kaestner, Anders, Willendrup, Peter K., Brüel, Annemarie, Sørensen, Henning Osholm, Thomsen, Jesper Skovhus, Schmidt, Søren, Poulsen, Henning Friis, Kuhn, Luise Theil, Birkedal, Henrik, Østergaard, Maja, Naver, Estrid Buhl, Kaestner, Anders, Willendrup, Peter K., Brüel, Annemarie, Sørensen, Henning Osholm, Thomsen, Jesper Skovhus, Schmidt, Søren, Poulsen, Henning Friis, Kuhn, Luise Theil, and Birkedal, Henrik

Abstract

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.

Published
2023

34. The FALCON double-detector Laue diffractometer add-on for grain mapping at POLDI

Author

Samothrakitis, Stavros, Larsen, Camilla Buhl, Kaestner, Anders, Polatidis, Efthymios, Čapek, Jan, Hovind, Jan, Fazan, Andrin, Allibon, John, Busi, Matteo, Schmidt, Søren, Kopeček, Jaromír, Strobl, Markus, Samothrakitis, Stavros, Larsen, Camilla Buhl, Kaestner, Anders, Polatidis, Efthymios, Čapek, Jan, Hovind, Jan, Fazan, Andrin, Allibon, John, Busi, Matteo, Schmidt, Søren, Kopeček, Jaromír, and Strobl, Markus

Published
2023

37. Microplastic Interaction with Soil Water - Visualization and Quantification with Neutron and X-ray Imaging

Author

Andreas Cramer, Pascal Benard, Kaestner Anders, Mohsen Zarebanadkouki, and Andrea Carminati

Abstract

Soil is considered the largest sink of microplastics (MP) in terrestrial ecosystems. Among the expected effects of MP as hydrophobic surface addition is the likelihood that MP enhances soil water repellency. So, crucial for MP fate in soils is the interaction between MP and water. If MP is translocated by water flow and, vice versa, MP impacts water flow, to what extent? Water flow on the pore scale will be impacted with feedbacks on transport and retention of MP. However, we don’t know the extent of and conditions under which MP are transported through porous media and, if deposited, how they interplay with soil water dynamics. We hypothesize that: (i) isolated MP are displaced and translocated by air-water interfaces and (ii) local accumulation of MP is facilitated by bypassing water flow. To approach this question, neutron and x-ray imaging of MP and water in soils was utilized.Dual neutron and x-ray imaging at the beamlines ICON (Paul-Scherrer-Institute) during repeated wetting-drying cycles was applied to trace MP-water interactions in aluminum cylinders filled with sand (0.7-1.2 mm) and MP (PET, 20-75 µm) in gravimetric contents of 0.35, 1.05 and 2.10%. The contents refer to static contact angle estimations of the mixtures resembling < 90°, 90° and > 90°. First, simultaneous neutron and x-ray tomography captured the initial dry MP configuration in samples. Subsequently, neutron radiographies of deuterated water flow through the sample of 1 ml min-1 were recorded for 200s. After drying, repeated tomography gave insights into MP translocation.Neutron and x-ray imaging results showed that regions of major MP content are water repellent. Water flow bypasses and MP is mainly retained. Resultant air entrapments lead to reduced water contents. In regions of minor MP content water can infiltrate. Here, the air-water interface collects isolated MP and shifts their distribution towards an enhanced accumulation.Extrapolation of these results to natural soil systems suggests that vertical transport of MP can be limited especially at hotspots of high MP contents. Water bypasses here. This might limit the water dependent degradation processes of MP due to reductions in hydrolysis, coating and colonization by microorganisms even elongating the process of natural attenuation.

Published
2023

47. The cork viewed from the inside

Author

Lagorce-Tachon, Aurélie, Karbowiak, Thomas, Loupiac, Camille, Gaudry, Alexandre, Ott, Frédéric, Alba-Simionesco, Christiane, Gougeon, Régis D., Alcantara, Valentin, Mannes, David, Kaestner, Anders, Lehmann, Eberhard, and Bellat, Jean-Pierre

Published
2015
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