Statistical Uncertainty in Quantitative Neutron Radiography

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

Microwave polarimetry based wood scanning

We describe a method to detect knots and faults in wood logs based on microwave measurements and the depolarising properties of wood. The depolarisation is an effect of the anisotropy in the dielectric properties of wood, which is caused by the fibre structure. The measurements are made in the frequency domain where a discrete reflec-tion spectrum is sampled. By transforming the frequency spectrum into the time domain the spatial distribution of the reflections appear. The wave is transmitted in a pure linear polarisation, tilted to 45° For each discrete frequency all available information is measured for the reflected wave and therefore it is possible to calculate the complex polarisation ratio and the state of polarisation which are the quantities containing the most visible information. The measurements are one dimensional and by combining measurements from different directions we create tomographic slice images of the inner structure of a log. Our measurements has showed the possibility to follow the extension of knots in a log using only a iso-surface visualisation. The used equipment is working at low intensity and is therefore virtually harm-less to human beings, furthermore it is portable and can be operated by one single person

Microwave polarimetry based wood scanning

We describe a method to detect knots and faults in wood logs based on microwave measurements and the depolarising properties of wood. The depolarisation is an effect of the anisotropy in the dielectric properties of wood, which is caused by the fibre structure. The measurements are made in the frequency domain where a discrete reflec-tion spectrum is sampled. By transforming the frequency spectrum into the time domain the spatial distribution of the reflections appear. The wave is transmitted in a pure linear polarisation, tilted to 45° For each discrete frequency all available information is measured for the reflected wave and therefore it is possible to calculate the complex polarisation ratio and the state of polarisation which are the quantities containing the most visible information. The measurements are one dimensional and by combining measurements from different directions we create tomographic slice images of the inner structure of a log. Our measurements has showed the possibility to follow the extension of knots in a log using only a iso-surface visualisation. The used equipment is working at low intensity and is therefore virtually harm-less to human beings, furthermore it is portable and can be operated by one single person

Microwave polarimetry tomography of wood

In this paper, we present a new microwave-based method to make images of fiber structure, e.g., to locate knots in wood. Evaluation of Maxwell's equations for an electromagnetic wave propagating in an anisotropic media (wood) shows that the polarization of the wave depends on the local fiber orientation in the sample. Experiments support the theoretical evaluation showing that knots can be followed in images of polarimetric parameters, reconstructed from multiple monostatic measurements. The equipment works at low intensity and is, therefore, virtually harmless to human beings; furthermore, it can be made portable and be operated by a single person.Copyright © 2005 IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Halmstads's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.</p

The XTRA Option at the NEUTRA Facility—More Than 10 Years of Bi-Modal Neutron and X-ray Imaging at PSI

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

Characterization of oriented microstructures through anisotropic small-angle scattering by 2D neutron dark-field imaging

Within neutron imaging, different methods have been developed with the aim to go beyond the conventional contrast modalities, such as grating interferometry. Existing grating interferometers are sensitive to scattering in a single direction only, and thus investigations of anisotropic scattering structures imply the need for a circular scan of either the sample or the gratings. Here we propose an approach that allows assessment of anisotropic scattering in a single acquisition mode and to broaden the range of the investigation with respect to the probed correlation lengths. This is achieved by a far-field grating interferometer with a tailored 2D-design. The combination of a directional neutron dark-field imaging approach with a scan of the sample to detector distance yields to the characterization of the local 2D real-space correlation functions of a strongly oriented sample analogous to conventional small-angle scattering. Our results usher in quantitative and spatially resolved investigations of anisotropic and strongly oriented systems beyond current capabilities

Observations on the zirconium hydride precipitation and distribution in Zircaloy-4

Hydride precipitation and distribution in hot-rolled and annealed Zircaloy-4 plate samples artificially induced by gaseous hydrogen charging were studied primarily by neutron tomography, scanning electron microscopy (SEM), and SEM-based electron backscattered diffraction techniques. The precipitated hydride platelet (δ-ZrH1.66) at a hydrogen pressure of 20 atm was found following the {111}δ-ZrH1.66//(0001) α-Zr with the surrounding α-Zr matrix. The microstructural characterization indicated that hydrides with a relatively uniform distribution were precipitated on the rolling-transverse section of the plate, whereas, on the normal-transverse section, a hydride concentration gradient was present with a dense hydride layer near the surface. Further, the neutron tomography investigations clearly identified the nonuniform spatial distribution of hydrides. Thin hydride layers preferentially formed on the sample surface, and the concentrated hydrides precipitating at the edges/corner of the sample were observed. The causes for the localized hydride accumulation were also discussed