Special Issue "Advances in Neutron Imaging"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Applied Physics".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 10261

Special Issue Editor

Prof. Dr. Wolfgang Treimer
E-Mail
Guest Editor
Department Mathematics, Physics & Chemistry, University of Applied Sciences Berlin, Luxemburger Str 10, 13353 Berlin, Germany
Interests: neutron imaging; polarized neutron imaging; neutron optics; neutron interferometry; ultra-small angle neutron scattering; superconductivity

Special Issue Information

Dear Colleagues,

This special issue on “Advances in Neutron Imaging” of Applied Sciences shall publish a wide range of scientific research activities for a broad audience. It presents new and important findings using neutron imaging, reflecting many important areas of research activities in different scientific fields. Welcome are review articles, results of interdisciplinary research, as well as the latest research results from various disciplines, carried out with neutron imaging, which appeal to a broad audience.

Prof. Dr. Wolfgang Treimer
Guest Editor

Manuscript Submission Information

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Keywords

  • neutron imaging in physics research
  • material sciences
  • non-destructive investigations
  • interdisciplinary sciences
  • neutron imaging of quantum phenomena

Published Papers (12 papers)

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Editorial

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Editorial
Special Issue Advances in Neutron Imaging
Appl. Sci. 2022, 12(3), 1187; https://doi.org/10.3390/app12031187 - 24 Jan 2022
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Abstract
This Special Issue of Applied Sciences, “Advances in Neutron Imaging”, is published at a time when the COVID-19 epidemic is emerging worldwide [...] Full article
(This article belongs to the Special Issue Advances in Neutron Imaging)

Research

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Article
Sparse-View Neutron CT Reconstruction Using a Modified Weighted Total Difference Minimization Method
Appl. Sci. 2021, 11(22), 10942; https://doi.org/10.3390/app112210942 - 19 Nov 2021
Cited by 1 | Viewed by 404
Abstract
Indirect neutron imaging is an effective method for nondestructive testing of spent nuclear fuel elements. Considering the difficulty of obtaining experimental data in a high-radiation environment and the characteristic of high noise of neutron images, it is difficult to use the traditional FBP [...] Read more.
Indirect neutron imaging is an effective method for nondestructive testing of spent nuclear fuel elements. Considering the difficulty of obtaining experimental data in a high-radiation environment and the characteristic of high noise of neutron images, it is difficult to use the traditional FBP algorithm to recover the complete information of the sample based on the limited projection data. Therefore, it is necessary to develop the sparse-view CT reconstruction algorithm for indirect neutron imaging. In order to improve the quality of the reconstruction image, an iterative reconstruction method combining SIRT, MRP, and WTDM regularization is proposed. The reconstruction results obtained by using the proposed method on simulated data and actual neutron projection data are compared with the results of four other algorithms (FBP, SIRT, SIRT-TV, and SIRT-WTDM). The experimental results show that the SIRT-MWTDM algorithm has great advantages in both objective evaluation index and subjective observation in the reconstruction image of simulated data and neutron projection data. Full article
(This article belongs to the Special Issue Advances in Neutron Imaging)
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Article
Microstructural Characterization of a Single Crystal Copper Rod Using Monochromatic Neutron Radiography Scan and Tomography: A Test Experiment
Appl. Sci. 2021, 11(16), 7750; https://doi.org/10.3390/app11167750 - 23 Aug 2021
Cited by 1 | Viewed by 578
Abstract
This paper reports the analysis of a single crystal copper rod aiming to characterize the microstructural features related to the homogeneity of the single crystal growth and the presence, shape and extension of spatially distributed misaligned grains or areas. The analytical method used [...] Read more.
This paper reports the analysis of a single crystal copper rod aiming to characterize the microstructural features related to the homogeneity of the single crystal growth and the presence, shape and extension of spatially distributed misaligned grains or areas. The analytical method used for such analysis is wavelength scan neutron radiography and monochromatic neutron tomography. Such methods allow determination of the extent of differently oriented single crystal areas, identifying the most part of the rod volume as a single domain. It was also possible to characterize the spatial distribution and the degree of alignment of local point-like or extended defects. Full article
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Article
Determination of the Spatial Resolution in the Case of Imaging Magnetic Fields by Polarized Neutrons
Appl. Sci. 2021, 11(15), 6973; https://doi.org/10.3390/app11156973 - 29 Jul 2021
Cited by 1 | Viewed by 441
Abstract
One of the most important parameters characterizing imaging systems (neutrons, X-rays, etc.) is their spatial resolution. In magnetic field imaging, the spatial resolution depends on the (magnetic) resolution of the depolarization of spin-polarized neutrons. This should be realized by different methods, but they [...] Read more.
One of the most important parameters characterizing imaging systems (neutrons, X-rays, etc.) is their spatial resolution. In magnetic field imaging, the spatial resolution depends on the (magnetic) resolution of the depolarization of spin-polarized neutrons. This should be realized by different methods, but they all have in common that a spin-polarizing and spin-analyzing system is part of the resolution function. First a simple and useful method for determining the spatial resolution for unpolarized neutrons is presented, and then methods in the case of imaging with polarized neutrons. Spatial resolution in the case of polarized neutron imaging is fundamentally different from ‘classical’ spatial resolution. Because of π-periodicity, the shortest path along which a spin-flip can occur is a measure of ‘magnetic’ spatial resolution. Conversely, the largest detectable magnetic field (B-field) within a given path length is also a measure of magnetic spatial resolution. This refers to the spatial resolution in the flight direction of the neutrons (Δy). The Δx and Δz refers to the spatial resolution in x- or z-direction; however, in these cases a different method must be used. Therefore, two independent methods are used to distinguish longitudinal and lateral spatial resolution, one method to determine the modulation transfer function (MTF) by recording the frequency-dependent fringe contrast of magnetic field images of a coil (longitudinal spatial resolution), and the second method, to observe the fringe displacement at the detector as a function of magnetic motion, provided that the accuracy of the motion is much better than the pixel size (at least half the pixel size) of the detector (lateral spatial resolution). The second method is a convolution of the fringe pattern with the pixel array of the detector. Full article
(This article belongs to the Special Issue Advances in Neutron Imaging)
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Article
Study of Possible Frequency Dependence of Small AC Fields on Magnetic Flux Trapping in Niobium by Polarized Neutron Imaging
Appl. Sci. 2021, 11(14), 6308; https://doi.org/10.3390/app11146308 - 08 Jul 2021
Cited by 2 | Viewed by 621
Abstract
Reducing the size of ambient magnetic flux trapping during cooldown in superconducting radio-frequency niobium cavities is essential to reaching the lowest power dissipation as required for continuous wave application. Here, it is suggested that applying an alternating magnetic field superimposed to the external [...] Read more.
Reducing the size of ambient magnetic flux trapping during cooldown in superconducting radio-frequency niobium cavities is essential to reaching the lowest power dissipation as required for continuous wave application. Here, it is suggested that applying an alternating magnetic field superimposed to the external DC field can potentially reduce the size of trapped flux by supporting flux line movement. This hypothesis is tested for the first time systematically on a buffered chemically polished (BCP) niobium sample before and after high temperature annealing, a procedure which is known to reduce flux pinning. External low-frequency (Hz-range) magnetic fields were applied to the samples during their superconducting transition and the effect of varying their amplitude, frequency and offset was investigated. A few results can be highlighted: The influence of the frequency and magnitude of the AC fields on the flux trapping in the untreated Nb sample cannot be neglected. The trapped flux seems to be homogeneously distributed, unlike the flux trapping in, e.g., lead (Pb), which is a type I superconductor. After annealing, the Nb sample shows practically no dependency of flux trapping on external AC fields. The trapped magnetic flux was measured by polarized neutron imaging, and calculations of trapped fields show good agreement with experimental results. Full article
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Article
The Bimodal Neutron and X-ray Imaging Driven by a Single Electron Linear Accelerator
Appl. Sci. 2021, 11(13), 6050; https://doi.org/10.3390/app11136050 - 29 Jun 2021
Cited by 1 | Viewed by 617
Abstract
Both X-ray imaging and neutron imaging are essential methods in non-destructive testing. In this work, a bimodal imaging method combining neutron and X-ray imaging is introduced. The experiment is based on a small electron accelerator-based photoneutron source that can simultaneously generate the following [...] Read more.
Both X-ray imaging and neutron imaging are essential methods in non-destructive testing. In this work, a bimodal imaging method combining neutron and X-ray imaging is introduced. The experiment is based on a small electron accelerator-based photoneutron source that can simultaneously generate the following two kinds of radiations: X-ray and neutron. This identification method utilizes the attenuation difference of the two rays’ incidence on the same material to determine the material’s properties based on dual-imaging fusion. It can enhance the identification of the materials from single ray imaging and has the potential for widespread use in on-site, non-destructive testing where metallic materials and non-metallic materials are mixed. Full article
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Article
Application of Machine Learning Methods to Neutron Transmission Spectroscopic Imaging for Solid–Liquid Phase Fraction Analysis
Appl. Sci. 2021, 11(13), 5988; https://doi.org/10.3390/app11135988 - 27 Jun 2021
Cited by 1 | Viewed by 1202
Abstract
In neutron transmission spectroscopic imaging, the transmission spectrum of each pixel on a two-dimensional detector is analyzed and the real-space distribution of microscopic information in an object is visualized with a wide field of view by mapping the obtained parameters. In the analysis [...] Read more.
In neutron transmission spectroscopic imaging, the transmission spectrum of each pixel on a two-dimensional detector is analyzed and the real-space distribution of microscopic information in an object is visualized with a wide field of view by mapping the obtained parameters. In the analysis of the transmission spectrum, since the spectrum can be classified with certain characteristics, it is possible for machine learning methods to be applied. In this study, we selected the subject of solid–liquid phase fraction imaging as the simplest application of the machine learning method. Firstly, liquid and solid transmission spectra have characteristic shapes, so spectrum classification according to their fraction can be carried out. Unsupervised and supervised machine learning analysis methods were tested and evaluated with simulated datasets of solid–liquid spectrum combinations. Then, the established methods were used to perform an analysis with actual measured spectrum datasets. As a result, the solid–liquid interface zone was specified from the solid–liquid phase fraction imaging using machine learning analysis. Full article
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Article
In Situ Neutron Radiography Investigations of Hydrogen Related Processes in Zirconium Alloys
Appl. Sci. 2021, 11(13), 5775; https://doi.org/10.3390/app11135775 - 22 Jun 2021
Cited by 2 | Viewed by 498
Abstract
In situ neutron radiography experiments can provide information about diffusive processes and the kinetics of chemical reactions. The paper discusses requirements for such investigations. As examples of the zirconium alloy Zircaloy-4, the hydrogen diffusion, the hydrogen uptake during high-temperature oxidation in steam, and [...] Read more.
In situ neutron radiography experiments can provide information about diffusive processes and the kinetics of chemical reactions. The paper discusses requirements for such investigations. As examples of the zirconium alloy Zircaloy-4, the hydrogen diffusion, the hydrogen uptake during high-temperature oxidation in steam, and the reaction in nitrogen/steam and air/steam atmospheres, results of in situ neutron radiography investigations are reviewed, and their benefit is discussed. Full article
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Article
Analysis and Mapping of Detailed Inner Information of Crystalline Grain by Wavelength-Resolved Neutron Transmission Imaging with Individual Bragg-Dip Profile-Fitting Analysis
Appl. Sci. 2021, 11(11), 5219; https://doi.org/10.3390/app11115219 - 04 Jun 2021
Cited by 2 | Viewed by 938
Abstract
As a new method for evaluating single crystals and oligocrystals, pulsed neutron Bragg-dip transmission analysis/imaging method is being developed. In this study, a single Bragg-dip profile-fitting analysis method was newly developed, and applied for analyzing detailed inner information in a crystalline grain position-dependently. [...] Read more.
As a new method for evaluating single crystals and oligocrystals, pulsed neutron Bragg-dip transmission analysis/imaging method is being developed. In this study, a single Bragg-dip profile-fitting analysis method was newly developed, and applied for analyzing detailed inner information in a crystalline grain position-dependently. In the method, the spectrum profile of a single Bragg-dip is analyzed at each position over a grain. As a result, it is expected that changes in crystal orientation, mosaic spread angle and thickness of a perfect crystal can be evaluated from the wavelength, the width and the integrated intensity of the Bragg-dip, respectively. For confirming this effectiveness, the method was applied to experimental data of position-dependent Bragg-dip transmission spectra of a Si-steel plate consisting of oligocrystals. As a result, inner information of multiple crystalline grains could be visualized and evaluated. The small change in crystal orientation in a grain, about 0.4°, could be observed by imaging the Bragg-dip wavelengths. By imaging the Bragg-dip widths, both another grain and mosaic block in a grain were detected. Furthermore, imaging results of the integrated intensities of Bragg-dips were consistent with the results of Bragg-dip width imaging. These small crystallographic changes have not been observed and visualized by previous Bragg-dip analysis methods. Full article
(This article belongs to the Special Issue Advances in Neutron Imaging)
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Article
Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography
Appl. Sci. 2021, 11(4), 1512; https://doi.org/10.3390/app11041512 - 08 Feb 2021
Cited by 3 | Viewed by 1041
Abstract
A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive [...] Read more.
A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth. Full article
(This article belongs to the Special Issue Advances in Neutron Imaging)
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Article
An Investigation of Radial Basis Function Method for Strain Reconstruction by Energy-Resolved Neutron Imaging
Appl. Sci. 2021, 11(1), 391; https://doi.org/10.3390/app11010391 - 03 Jan 2021
Cited by 2 | Viewed by 1268
Abstract
The main objective of the current work is to determine meshless methods using the radial basis function (rbf) approach to estimate the elastic strain field from energy-resolved neutron imaging. To this end, we first discretize the longitudinal ray transformation with rbf [...] Read more.
The main objective of the current work is to determine meshless methods using the radial basis function (rbf) approach to estimate the elastic strain field from energy-resolved neutron imaging. To this end, we first discretize the longitudinal ray transformation with rbf methods to give us an unconstrained optimization problem. This discretization is then transformed into a constrained optimization problem by adding equilibrium conditions to ensure uniqueness. The efficiency and accuracy of this approach are investigated for the situation of 2d plane stress. In addition, comparisons are made between the results obtained with rbf collocation, finite-element (fem) and analytical solution methods for test problems. The method is then applied to experimentally measured continuous and discontinuous strain fields using steel samples for an offset ring-and-plug and crushed ring, respectively. Full article
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Review

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Review
The XTRA Option at the NEUTRA Facility—More Than 10 Years of Bi-Modal Neutron and X-ray Imaging at PSI
Appl. Sci. 2021, 11(9), 3825; https://doi.org/10.3390/app11093825 - 23 Apr 2021
Cited by 3 | Viewed by 663
Abstract
Just after the start into the new millennium the concept for combined neutron and X-ray imaging was introduced by extending the standard configuration of the thermal neutron imaging NEUTRA instrument with a complementary 320 kV X-ray tube setup. Using essentially the same detector [...] Read more.
Just after the start into the new millennium the concept for combined neutron and X-ray imaging was introduced by extending the standard configuration of the thermal neutron imaging NEUTRA instrument with a complementary 320 kV X-ray tube setup. Using essentially the same detector configuration for both neutron and X-ray imaging enables a pixel-wise (in radiography) and a voxel-wise (in tomography) correlation and combination of attenuation data. The optimal use and analyses of such complementary data sets depend on the specific investigation and research question and range from a combinatory interpretation of separately analyzed images to full data fusion approaches. Here, several examples from more than a decade of bimodal neutron and X-ray imaging at NEUTRA at PSI shall be reviewed. Full article
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