Gabriel Frei

• Paul Scherrer Institute

The beamline for Imaging with COld Neutrons (ICON) at Swiss spallation neutron source (SINQ) at Paul Scherrer Institut has a flexible design to meet the requests from a wide user community. The current status of the beamline and its characteristics are described. The instrumentation includes three experimental positions from which two are equipped...

PSI has a relatively long tradition in neutron imaging since the first trials were done at its formerly existing research reactor SAPHIR with film methods. This reactor source was replaced after its shutdown in 1994 by the spallation neutron source SINQ in 1996, driven by the 590MeV cyclotron for protons with presently up to 2.3mA beam current.One...

Mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in polymer electrolyte fuel cell (PEFC). The four types of GDLs (Paper, Cloth, New structure with hydrophilic and hydrophobic layers and paper with MPL) were evaluated as specimens. The images of liquid water distribution in the GDLs were taken by neu...

A simplified, miniaturized polymer electrolyte fuel cell without gas diffusion layers was investigated under operation by neutron radiography. By visualizing liquid water, it was possible to identify limiting effects, which are directly related to the simplified construction principle. Depending on the operation conditions, undesired water accumula...

Improvements in the spatial resolution of neutron imaging were specifically developed for application in fuel cell imaging, where the resolution requirement in different directions may vary by 1 order of magnitude, thus making anisotropic setups attractive. A maximal spatial resolution of 8.7 mu m could be reached. For the transient studies, the co...

Neutron imaging as method for non-destructive studies profits from the alternative contrast mechanism compared to X-rays: most of the light elements enable high contrast whereas heavy elements are relatively transparent for neutrons. This article gives a short overview about PSI's activities in this promising and still developing field with high po...

Crystalline materials show a scattering behaviour in the energy range below 10 meV when the Bragg condition is fulfilled for lattice planes in the crystals. Investigations with a neutron imaging method require the energy bands narrowed more than for the polychromatic spectrum emitted by the cold source. This approach was used in the present work fo...

A new setup for stationary neutron imaging with highest possible resolution, based on the light detection from a neutron-sensitive scintillator screen with a dedicated lens coupled to a cooled CCD was completed recently. Although, some first test results have already been reported (E.H. Lehmann, et al., Nucl. Instr. and Meth. A 576(2–3) (2007) 389)...

The aim of the current study is on water distribution inside and near the gas diffusion layers around the membrane (“in-plane” study). Because this region is normally only about 200μm wide, a very high spatial resolution is required for this kind of studies.PSI managed to build a neutron imaging setup with a stationary detection system providing be...

Edge enhancement is the main effect measured by the so-called inline or propagation-based neutron phase contrast imaging method. The effect has originally been explained by diffraction, and high spatial coherence has been claimed to be a necessary precondition. However, edge enhancement has also been found in conventional imaging with high resoluti...

In the past, neutron imaging investigations have been mostly performed in “integrating mode”, which averages over the full applied neutron energy spectrum. This article describes four different methods and devices of obtaining energy selectivity in the thermal to cold energy range, which allow a new approach in neutron imaging. Two principles have...

We report on how a neutron grating interferometer can yield projection images of the internal domain structure in bulk ferromagnetic samples. The image contrast relies on the ultrasmall angle scattering of unpolarized neutrons at domain wall structures in the specimen. The results show the basic domains of (110)-oriented sheets in an FeSi test samp...

The temporal and spatial distribution of water within a porous medium is affected by the medium’s structure, i.e., the spatial arrangement of its constituents. To analyze structural effects on the fluid dynamics, we measured the 3D water content distribution in a heterogeneous sand column during two drainage-wetting cycles using neutron transmissio...

High resolution neutron radiography was used to observe the time resolved distribution of 2H nuclei in the membrane of an operating polymer electrolyte fuel cell (PEFC) after changing the anode gas from 1H2 to 2H2. The rate of replacement and the distribution of 2H nuclei shortly after the change of the anode gas were found to be independent of the...

The mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in PEFC. In this study, following simultaneous measuring method was tried out, namely, the oxygen diffusivity of porous media with moisture was measured by using an experimental apparatus consist of oxygen sensor based on galvanic battery, and liq...

Here we introduce a novel neutron imaging method, which is based on the effect that the spatial coherence of the neutron wave front can be changed through small-angle scattering of neutrons at magnetic domain walls in the specimen. We show that the technique can be used to visualize internal bulk magnetic domain structures that are difficult to acc...

We have developed a neutron phase contrast imaging method based on a grating interferometer setup. The principal constituents are two absorption gratings made of gadolinium and a phase modulating grating made of silicon. The design parameters of the setup, such as periodicity, structure heights of the gratings, and the distances between the grating...

The water distribution across the membrane electrolyte assembly (MEA) of a working polymer electrolyte fuel cell (PEFC) was observed in situ using neutron radiography. In order to resolve the distribution between the different layers of the MEA, in plane imaging (cell membrane parallel to the beam) was used. Unprecedented spatial resolution for neu...

Neutron imaging as a modern inspection and research tool is nowadays based on digital systems. One of the key components, converting the neutron field into detectable photons, is a suitable scintillation screen. Hereby, the initial detection process is the capture of the neutrons within a strongly absorbing converter material. The secondary radiati...

Energy selection in neutron radiography provides a means for contrast enhancement and contrast variation, mainly based on the Bragg edge fluctuations of the total neutron cross sections of materials. At a steady state neutron source energy bands can be selected using high-speed rotors or single-crystal monochromators whereas at a pulsed neutron sou...

The mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in PEFC. In this study, the oxygen diffusivity of paper and cloth type porous media used generally as GDL with respect to its liquid water content were measured by using an experimental apparatus consist of oxygen sensor based on Galvanic battery,...

Energy-selective neutron radiography experiments were carried out at the ISIS pulsed spallation source. This neutron transmission imaging technique combines the hardware used for conventional neutron radiography with the Bragg edge transmission features of time-of-flight methods. The main component of the energy-selective radiography set-up was a g...

To overcome present limitations of the spatial resolution in neutron imaging a newly designed setup was realized at the ICON facility [G. Kühne et al., ICON—the new facility for cold neutron imaging at the Swiss spallation neutron source SINQ, Swiss Neutron News 28 (December 2005), pp. 20–29, 〈http://sgn.web.psi.ch/sgn/snn/snn_28.pdf〉], which is in...

We report on the fabrication and application of a novel neutron imaging test device made of gadolinium. It is designed for a real time evaluation of the spatial resolution, resolution direction, and distortions of a neutron imaging detector system. Measurements of the spatial resolution of (6)LiF doped ZnS scintillator screens with different thickn...

Based on experience from many kinds of investigations with neutron imaging methods (radiography, tomography, time-dependent studies) and in comparison to conventional X-ray methods, the authors discuss the potential of future improved studies for cultural-heritage purposes. Whereas the focus of the paper is on the imaging aspect, other established...

Neutron transmission tomography is a technique providing two- or three-dimensional maps of the attenuation coefficient distribution within an object. By this means, the inner macroscopic structure and material composition can be visualized. Although basic principles are known since decades, this technique became more used in recent time, due to the...

DOI:https://doi.org/10.1103/PhysRevLett.97.069905

We report how a setup consisting of three gratings yields quantitative two- and three-dimensional images depicting the quantum-mechanical phase shifts of neutron de Broglie wave packets induced by the influence of macroscopic objects. Since our approach requires only a little spatial and chromatic coherence it provides a more than 2 orders of magni...

A new non-destructive method based on neutron imaging (neutron radiography) to determine the exact water content in aramid-based soft body armour panels is presented. While investigating the ballistic resistance of aramid-based body armour panels under a wet condition, it is important to precisely determine their water content and its chronological...

Based on the very good experience and knowledge gained with thermal neutron radiography at NEUTRA, novel capabilities can be predicted for a new beamline with cold neutrons: Micro tomography, neutron phase contrast imaging, contrast enhanced radiography, improved quantification of tracer elements and energy selective neutron imaging.The two main co...

Generating electricity via electrochemical conversion of chemical energy within a fuel cell is a very promising approach, which is investigated in many laboratories worldwide. Although the fuel cell principle has been known since many years, dedicated studies are needed to make this technology competing and cost efficient. Especially, low-temperatu...

Neutron radioscopy, or dynamic neutron radiography, is a non-destructive testing method, which has made big steps in the last years. Depending on the neutron flux, the object and the detector, for single events a time resolution down to a few milliseconds is possible. In the case of repetitive processes the object can be synchronized with the detec...

When time-dependent processes within metallic structures should be inspected and visualized, neutrons are well suited due to their high penetration through Al, Ag, Ti or even steel. Then it becomes possible to inspect the propagation, distribution and evaporation of organic liquids as lubricants, fuel or water. The principle set-up of a suited real...

Today's neutron sources do not deliver sufficient flux to examine singular short-time events in the millisecond range by neutron radiography.However, periodic processes can be examined if a triggered accumulating detector collects information of identical time-windows and positions over several cycles of the process. The same problem applies if the...

Commonly applied imaging methods in neutron radiography use a CCD camera in conjunction with a scintillator or imaging plates. CCDs and imaging plates have desirable properties concerning resolution, linearity, dynamic range and signal-to-noise ratio (S/N) but both techniques have the disadvantage of a slow read out and for the CCD camera, an addit...

Properties of the cold-neutron beam at the FUNSPIN facility of the SINQ neutron source of the Paul Scherrer Institute, Villigen, Switzerland were investigated. The measured flux density Phi = (2.46 +/- 0.04) x 10(8) [cm(2) s mA](-1), the wavelength averaged mean polarization around the beam axis P-A = (95.29 +/- 0.04)% and the mean polarization ove...

This article describes the status of neutron imaging with the focus on the detection systems in use, mainly based on a digital approach. When intense pulsed will be available in the near future, neutron imaging can take profit too by applying energy selective and triggered “flash” methods for dedicated investigations. Therefore, the layout, specifi...

This paper gives an overview about the investigation of technical objects and processes by different neutron radiography methods in order to solve several tasks and problems nondestructively. It is important to mention that for each problem, the approach was tried which seemed to be best suited. This was possible due to the high flexibility in resp...

Neutrons with the initial energy of 14 MeV produced by the neutron generator of the Department of Reactor Physics, Chalmers University of Technology, Göteborg, Sweden, were detected by a camera system in connection with scintillator screens. Images were produced for 14 MeV and moderated neutrons with suited scintillator screens. Qualitative and qua...

For many years, the major detection system for neutron radiography consisted in an X-ray film, where the conversion from neutrons to detectable radiation was made with a metallic layer of Gd, Dy or In. With this method, high spatial resolution was achieved, only limited by the beam properties of the radiography facilities.This situation has changed...

Neutron radiography is used to study moisture transport in textiles for the first time. A selection of clothing systems composed of layers with differing water transport properties is studied to demonstrate the feasibility of using the technique. The results are compared to the weights of the individual layers obtained during separate sets of measu...

Due to the high transmission of thermal neutrons through uranium, plutonium and thorium, non-irradiated nuclear fuel can easily be inspected concerning defects, homogeneity and enrichment. Especially when so-called "burnable poisons" are added to the pellets (used for the prolongation of the fuel cycles in NPP's), the non-destructive manufactory co...

We report how an interferometic method can produce quantitative x-ray and neutron phase contrast images. The interferometer is based on diffraction gratings fabricated using microlithography techniques. Separate phase and absorption images are recorded simultaneously (1). By taking data sets under many viewing angles, a tomographic reconstruction o...

Adhesive bonding or sealing applications are increasingly used in many technical areas: for example in mechanical engineering, in the car industry, the aircraft industry, wood or paper industry, etc. The advantages of this method are manifold if it is used correctly. There is a growing demand for non-destructive testing of new bonding products and...