A new method to obtain the crystallographic texture of polycrystalline materials in Bragg edge imaging experimentsAlvarez, M A Vicente; Malamud, Florencia
doi: 10.1088/1742-6596/2605/1/012023pmid: N/A
In polycrystalline materials, the shape and height of Bragg edges observed in wavelength resolved neutron transmission experiments depend on the crystallographic texture. Previous works have proved the capacity of actual models to predict the transmission spectra once the texture of the material is known. In this work, we summarize the recent advances done trying to obtain information of the texture from the experimental transmission data. The basis of this method resides in a compact expression of the coherent elastic cross section in terms of the Fourier coefficients of the orientation distribution function, which describes the crystallographic texture. The validity of this method is restricted to the applicability of the kinematic approximation of diffraction (polycrystalline materials with grain sizes below 10μm) and to materials with spatially uniform texture.
ASTOR: the imaging beamline of the Argentine Neutron Beam LaboratoryVega, N A; Bertalot, F M; Bazzana, S; Peirone, M; Santisteban, J
doi: 10.1088/1742-6596/2605/1/012007pmid: N/A
The ASTOR instrument is a state-of-the-art neutron imaging instrument being developed by LAHN (Laboratorio Argentino de Haces de Neutrones or Argentinian Laboratory of Neutron Beams) to be installed on one of the cold neutron beams of the 30MW open pool reactor RA-10, currently under construction at the outskirts of Buenos Aires. ASTOR will have direct view to a D2 cold source and will include a primary collimator at 2.5m from its surface. Its design includes a beam conformation room with a set of exchangeable secondary collimators to further collimate the beam, and several devices (solid state filters, a velocity selector and a double crystal monochromator) to tailor the energy spectrum for specific applications. Downstream the beam, it will have an experimental room with ample space for objects and samples, and L/D ratios in the range 120-1500 with calculated fluxes of 3.7x108 n/cm2s and 2.4x106 n/cm2s respectively (E<25meV) and a maximum field of view of 25x25 cm2. It will also count with two rectangular pinholes to obtain increased resolution in one dimension without substantially decreasing the flux.
Flexible camera detector box design using 3D printersSchillinger, B; Geerits, N; Jünger, T; Matoušková, J; Neuwirth, T; Oppermann, F; Sebold, S; Sponar, S
doi: 10.1088/1742-6596/2605/1/012008pmid: N/A
In the early days of electronic neutron imaging, the best available and most expensive components were used to build detectors. Experience has shown that only few parameters are truly important, so we have built a whole new line of specialized neutron imaging detectors based on astronomy cameras and 3D printed housings with external shielding. As an additional benefit, 3D printed housings produce no gammas on neutron capture, and provide nearly spot-free images. Plans and print files for 3D printed detectors are available for free on request.
Update of Bragg edge analysis software “GUI-RITS”Oikawa, K; Sato, H; Watanabe, K; Su, Y H; Shinohara, T; Kai, T; Kiyanagi, Y; Hasemi, H
doi: 10.1088/1742-6596/2605/1/012013pmid: N/A
The energy-resolved neutron imaging system, RADEN at J-PARC, has been providing to users a Rietveld-type analysis code, RITS, for pulsed neutron Bragg-edge transmission (BET) imaging with a graphical user interface (GUI) version, for fitting spectral data obtained with this instrument. In the last year, we updated the computational platform of GUI-RITS software from Scientific Linux 6 (SL6) and Python 2 to Windows 10 and Python 3, and added some functions to improve usability. The license agreement for this updated software is the Berkeley Software Distribution (BSD) 2-Clause License (non-copyleft) and is currently available for download from the RADEN website.
New Measurements on Borated Neutron Imaging Screens at Budapest Neutron Centre (BNC)Schillinger, B; Chuirazzi, W; Cool, S; Craft, A; Kis, Z; Szentmiklósi, L; Tengattini, A
doi: 10.1088/1742-6596/2605/1/012009pmid: N/A
The most commonly used screens for neutron imaging consist of 6LiF+ZnS. This type of screen yields the highest light output per detected neutron. For high resolution, gadolinium-oxisulfide (Gadox) screens are employed, which have a much higher detection efficiency, but a light output much lower than LiF+ZnS that measurements are often limited by photon statistics. Screens using boron as neutron sensitive material have not been very successful in the past but recently, a new preparation method was introduced that combines light output 5-6 times higher than Gadox with detection efficiency larger than LiF+ZnS. Previous measurements were performed at FRM II, Garching, and ILL, Grenoble, which already matched a Gadox screen in resolution, but still contained too many inhomogeneities in the detector material’s grains to produce an optimized detector. We report about the most recent measurements of new borated screens produced with an improved milling process at the NORMA facility at Budapest Neutron Centre (BNC), in comparison to a high resolution Gadox screen.
Design of a hydrogen storage device for evaluating tensions induced by volumetric expansion during hydrogen absorptionMarín, J; Biasetti, A; Meyer, G; Borzone, E M; Aversente, N; Baruj, A
doi: 10.1088/1742-6596/2605/1/012034pmid: N/A
Hydride-Forming Materials (HFM) allow the storage of hydrogen in solid state. The reaction can be reversed by delivering heat or lowering pressure, releasing gaseous hydrogen. When hydrogen is incorporated into its structure, the HFM experiences a volumetric expansion. In the case of LaNi5, a commonly studied AB5 type material, it can be as high as 25%. This mismatch produces stress within the material, which breaks apart. Successive cycles produce further decrepitation into a fine powder, which reduces heat transfer, and compaction, which affects diffusion of the gas phase and, in extreme cases, may deform or even break the container. For these reasons, in order to make a safe and efficient hydrogen storage system it is of crucial importance to characterize the volumetric expansion and the mechanical stress originated by the HFM. With these objectives, we have designed a device with an adequate geometry for being studied by neutron imaging. This technique allows to observe the interior of a metallic vessel and, at the same time, to distinguish the hydrogen distribution in a HFM through a convenient contrast difference. Furthermore, we have designed and manufactured a mechanical indicator of the volume changes caused by cycling and allows their direct observation.
A work-horse neutron imaging station at the Laboratorio Energia Nucleare Applicata (LENA) in Pavia (Italy): Instrumental components and applications in the frame of the CHNet-NICHE INFN experiment.Grazzi, F; Cantini, F; Sans-Planell, O; Magalini, M; Vigorelli, L; Marcucci, G; Clemenza, M; Morigi, M; Re, A; Alloni, D; Prata, M; Gelli, N
doi: 10.1088/1742-6596/2605/1/012006pmid: N/A
In this work, achieved results on the NICHE project (Neutron Imaging in Cultural HEritage) are presented. It fits in the frame of the Cultural Heritage Network (CHNet) of the Italian Nuclear Physics Institute (INFN), and is devoted to the development and usage of a new neutron imaging station on the thermal port of the 250 kW TRIGA Mark-II reactor installed in the Laboratorio Energia Nucleare Applicata (LENA) in Pavia (Italy). The application of neutron radiography to the diagnostic in the cultural heritage field is quite widespread among the research community since it is a non-invasive technique which allows for revealing of the inner structure of the investigated objects, the identification of different materials and their relative spatial distribution with a suitable level of resolution and contrast. We present here the status and progresses within the project: technical characteristics of the beamline and the imaging station component, measuring configuration, possible applications, and examples.
Tomographic reconstruction with Mantid ImagingTygier, S; Akello-Egwel, D; Allen, J; Baust, R; Bradley, J; Burca, G; Fedrigo, A; Gigg, M; Jones, S; Kockelmann, W; Nixon, D; Pooley, D E; Tasev, D
doi: 10.1088/1742-6596/2605/1/012017pmid: N/A
Mantid Imaging has been developed to provide a graphical reconstruction process for users of neutron imaging instruments to eliminate the need to fall back on commercial software. Mantid Imaging builds on algorithms provided by libraries including Astra Toolbox and Tomopy to offer noise reduction, artifact removal, alignment, filtered back projection and iterative reconstruction methods. Extra functionality was added by using algorithms from ALGOTOM for ring removal and from the Core Imaging Library (CIL) for regularised 3D reconstruction.Mantid Imaging 2.4 has recently been released. It is an open source Python GUI, runs under Linux and Windows and can easily be installed on end user systems. Mantid Imaging is aimed at users with no programming background and with little image processing experience. At ISIS Mantid Imaging runs on the ISIS-Data-Analysis-as-a-Service (IDAaaS) platform, which is remotely accessible with any modern web browser and gives users access to sufficient hardware resources to handle large datasets. Extensions of Mantid Imaging for energy-resolved neutron imaging are planned for the future.
Time-of-flight polarization contrast neutron imaging for enhanced characterization of ferritic phase fractions in Fe-Mn-Si shape memory alloysBusi, Matteo; Ferretto, Irene; Malamud, Florencia; Leinenbach, Christian; Strobl, Markus
doi: 10.1088/1742-6596/2605/1/012025pmid: N/A
The determination of the amount and distribution of different phase fractions in additively manufactured shape memory alloys processed with laser powder bed fusion is crucial for understanding the correlation between processing parameters, microstructure, and mechanical properties. Neutron imaging techniques, such as Bragg edge imaging and polarization contrast neutron imaging (PNI), have been introduced to complement and overcome the limitations of traditional characterization methods, which are often destructive and limited to surface analyses and small-sized specimens. Bragg edge imaging can distinguish and quantify crystallographic phase fractions with spatial resolutions of a few tens of micrometers, while PNI is highly sensitive to crystallographic phases and is particularly suited for sub-percent phase fractions and in-situ, time-resolved, and tomographic analyses. In this work, we present a time-of-flight PNI method that enables simultaneous measurements of phase fractions.
Hydrogen diffusion in Zr-2.5Nb pressure tubes specimens between 300°C-400°C by in-situ neutron imaging experimentsStella, V.M.; Soria, S.R.; Gomez, A.; Grosse, M.; Schulz, M.; Santisteban, J. R.
doi: 10.1088/1742-6596/2605/1/012037pmid: N/A
Zirconium (Zr) alloys are widely used in nuclear power plants as fuel cladding and are susceptible to hydrogen (H) degradation. For long operational service, Zr-based components can suffer a mechanism known as Delayed Hydride Cracking (DHC) associated to an increase of the crack propagation velocity by the re-orientation and precipitation of Zr hydride. In this process, the H mobility has a great influence. In the present work, the isothermal diffusion of H in Zr-2.5%Nb specimens obtained from a CANDU pressure tube were studied at consecutive temperatures of 300°C, 350°C, 375°C and 400°C. H content and mobility were quantified by in-situ neutron imaging experiments performed on ANTARES, the cold neutron imaging facility of FRM II. The time evolution of the H concentration across the specimen allowed the determination of diffusion coefficients, and an assessment of the limitations of existing models commonly used to describe H diffusion.