Application of an iterative artefact reduction method to neutron tomography

Kasperl, Stefan; Vontobel, Peter

doi:10.1016/j.nima.2005.01.167

Cited by 17 publications

(9 citation statements)

References 2 publications

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“…In neutron imaging, the bulk properties of materials can be calculated when the attenuation in the object is described quantitatively. The exponential law of attenuation (Beer‐Lambert) can be applied directly according to (equation ) [ Kasperl and Vontobel , ]. The transmitted intensity I of the uncollided neutron beam is

I = I_{0} e^{- Σ d}

where I 0 is the intensity of the beam before it enters the sample, I is the intensity of the beam after it passes through the sample, the attenuation coefficient Σ (cm −1 ) comprises the atom density and the microscopic cross sections associated with various interactions of neutrons passing through the object of the thickness d (cm).…”

Section: Methodsmentioning

confidence: 99%

Water and entrapped air redistribution in heterogeneous sand sample: Quantitative neutron imaging of the process

Sněhota

Jelínková

Sobotková

et al. 2015

Water Resources Research

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Saturated flow in soil with the occurrence of preferential flow often exhibits temporal changes of saturated hydraulic conductivity even during the time scale of a single infiltration event. These effects, observed in a number of experiments done mainly on heterogeneous soils, are often attributed to the changing distribution of water and air in the sample. We have measured the variation of the flow rates during the steady state stage of the constant head ponded infiltration experiment conducted on a packed sample composed of three different grades of sand. The experiment was monitored by quantitative neutron imaging, which provided information about the spatial distribution of water in the sample. Measurements were taken during (i) the initial stages of infiltration by neutron radiography and (ii) during the steady state flow by neutron tomography. A gradual decrease of the hydraulic conductivity has been observed during the first 4 h of the infiltration event. A series of neutron tomography images taken during the quasi-steady state stage showed the trapping of air bubbles in coarser sand. Furthermore, the water content in the coarse sand decreased even more while the water content in the embedded fine sand blocks gradually increased. The experimental results support the hypothesis that the effect of the gradual hydraulic conductivity decrease is caused by entrapped air redistribution and the build up of bubbles in preferential pathways. The trapped air thus restricts the preferential flow pathways and causes lower hydraulic conductivity.

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I = I_{0} e^{- Σ d}

Section: Methodsmentioning

confidence: 99%

Water and entrapped air redistribution in heterogeneous sand sample: Quantitative neutron imaging of the process

Sněhota

Jelínková

Sobotková

et al. 2015

Water Resources Research

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“…Neutron radiography techniques (and others such as X‐ray) are based on the exponential law (similar to the Lambert–Beer law) of attenuation of radiation passing through matter (Kasperl and Vontobel, 2005):

\begin{matrix} {I = B I}_{0} exp (- Sd) \end{matrix}

where I is the attenuated neutron flux (neutrons m −2 s −1 ) obtained from an incident neutron flux I 0 passing through a material of thickness d (m) with an attenuation coefficient S (m −1 ). B is a factor modifying the intensity I recorded at the detector to account for a number of other contributions, such as from scatter neutrons.…”

Section: Methodsmentioning

confidence: 99%

Quantitative Imaging of Infiltration, Root Growth, and Root Water Uptake via Neutron Radiography

Oswald

Menon

Carminati

et al. 2008

Vadose Zone Journal

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117

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Water infiltration into vegetated soils is affected by interactions between soil properties and plant activity. Water uptake by plant roots depends on the soil hydraulic properties and infiltration rate. In turn, roots are important water movers and induce nonuniform water content distributions with consequent impact on the infiltration rate. Our goal was to use neutron radiography to investigate root water uptake during rapid infiltration events and subsequent water redistribution. Neutron radiography is an imaging technique capable of measuring with high spatial and temporal resolution root density, soil structure, and water distributions in the vicinity of roots. We used time‐series neutron radiography to image infiltration events in 0.17‐ by 0.15‐ by 0.013‐m boxes filled with a sand mixture and that contained either lupine (Lupinus L.) or maize (Zea mays L.) plants. We measured four replications at two stages of plant growth. Neutron radiography can detect small variations in water content with high accuracy and high spatial and temporal resolution. Due to their high water content, roots were easily visible in the radiograms before infiltration. Following calibration, we quantified the water content in the sample during and after each infiltration event. Effects of soil heterogeneities such as thin soil layers were visible, as was water uptake by roots. We observed lower water contents along the main root of lupine during the early stage of infiltration, and slower and more diffuse uptake during the later stages of water redistribution, when the wetting front had propagated downward and the water content in the soil decreased. The observed root water uptake was not uniform but rather was localized in certain regions. For maize we observed a loss of water mainly in the upper part of the root system, closer to the stem rather than at root tips.

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“…Radiography techniques (X-ray or NR) are based on the exponential law (similar to the Lambert-Beer law) of attenuation of radiation passing through matter (Kasperl & Vontobel, 2005):…”

Section: Introductionmentioning

confidence: 99%

Visualization of root growth in heterogeneously contaminated soil using neutron radiography

Menon

Robinson

Oswald

et al. 2006

European J Soil Science

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We used neutron radiography (NR), a non-invasive and in situ technique, to study living plant roots in soil. Plant roots have a larger water content than their unsaturated surrounding media. As water strongly attenuates a neutron-beam, NR can identify root structures in detail. We investigated the use of NR to visualize the root growth of lupin in quartz sand and in a loamy sand field soil. Further experiments elucidated the root growth of lupin in the loamy sand heterogeneously contaminated with 10 and 20 mg kg À1 boron (B) and 100 mg kg À1 zinc (Zn). We obtained high-quality images of root growth dynamics in both media with a resolution range of 110-270 mm. The images with quartz sand revealed fine structures such as proteoid roots that are difficult to locate in situ by other methods without destruction of the soil. Though quartz sand provided excellent visibility of roots, it proved to be a poor medium for growing plants, probably because of its bulk density (1.8 Mg m À3 ). The images with field soil showed normal root growth with slightly less contrast than the quartz sand. The poorer contrast was due to the greater neutron interaction with soil water and soil organic matter. In the heterogeneously contaminated soil, root growth was significantly reduced in the contaminated part of the soil in all B and Zn treatments. This study shows that NR has potential as a non-invasive method to investigate root growth over time as well as the response of roots to various abiotic stress factors.

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Application of an iterative artefact reduction method to neutron tomography

Cited by 17 publications

References 2 publications

Water and entrapped air redistribution in heterogeneous sand sample: Quantitative neutron imaging of the process

Water and entrapped air redistribution in heterogeneous sand sample: Quantitative neutron imaging of the process

Quantitative Imaging of Infiltration, Root Growth, and Root Water Uptake via Neutron Radiography

Visualization of root growth in heterogeneously contaminated soil using neutron radiography

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