Neutron Imaging Facility Research Articles

ANTARES: Cold neutron radiography and tomography facility

The neutron imaging facility ANTARES, operated by the Technische Universität München, is located at the cold neutron beam port SR-4a. Based on a pinhole camera principle with a variable collimator located close to the beam port, the facility provides the possibility for flexible use in high resolution and high flux imaging.

Simultaneous Neutron and x-Ray Tomography for Advanced Battery Research

The current demand of high powered portable electronics and electric vehicles has put significant strain on current battery technology. To improve performance of advanced battery technologies, such as lithium-air, it is critical to understand how reactive species transport and distribute throughout the cell at varying states of charge. Neutron and x-ray imaging techniques allow in-situ visualization of reactants within the battery. X-ray attenuation increases with increasing atomic number while neutron attenuation is more random with strong attenuation by lithium. These techniques can provide complementary data by providing critical microstructure information. To provide access to both techniques, NIST is developing a simultaneous neutron and x-ray imaging facility. The new system orients a 90 keV microfocus x-ray source 90° to the neutron beam to allow for simultaneous tomography as shown in Figure 1. This x-ray system will allow for variable energy, brilliance, and magnification while matching the neutron spatial resolution of 15-50 micron. Matching image resolution of the two beams will allow the overlaying of the two tomograms. Simultaneously imaging batteries will allow reaction species, such as lithium, and solid structure to be resolved at identical conditions which can’t be guaranteed for serial imaging (possibly at different facilities). This presentation will describe the new simultaneous imaging system and evaluate its measurement uncertainties while assessing its abilities using an assortment of batteries including alkaline, Ni-Cd, and Li-ion. Figure 1

Influence of Thermal Conductivity and 2-D Temperature Distribution of Liquid Water Saturation

For use in automotive power, polymer electrolyte fuel cells are being pushed to ever higher levels of performance and efficiency. At these high performance levels, large thermal gradients can exist across the diffusion media. These large gradients can have a strong influence on water transport in the cell via phase-change-induced flow and thermally driven diffusion. The focus of this work is to elucidate the effects of diffusion media thermal conductivity on through-plane 2-D temperature and saturation distributions. Neutron imaging was conducted at the NIST Center for Neutron Research BT-2 neutron imaging facility and used to measure how saturation levels were influenced by the internal heat generation and temperature distributions. A custom 4.8 cm2 fuel cell with precision liquid coolant temperature control was used for the high resolution through-plane radiography. The precision liquid coolant ensures stable, high accuracy thermal boundary conditions for the analysis. Temperature distributions were computed in COMSOL using experimentally measured dry and wet thermal conductivity values for commercial diffusion media. These temperature distributions were then coupled to the measured saturation distributions from neutron imaging to determine the relationships between level of saturation and temperature gradient as shown in Figure 1. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EERE supported program (Award Number DE-EE0000470). Additional funding provided by Department of Energy interagency agreement No. DEAI01-01EE50660. Figure 1

Design of a Thermal Neutron Beam for a New Neutron Imaging Facility at Tehran Research Reactor

A new neutron imaging facility will be built around the Tehran Research Reactor (TRR). The TRR is an open pool light water moderated5 MW research reactor with six beam tubes. The neutron energy spectrum near the reactor core at the entrance of the beam tube was measured by the foil activation method using the SAND-II code and calculated by the MCNP Monte Carlo code. There was a good similarity between calculated and simulated spectra. The principal component of this facility is its neutron collimator. The collimator is a beam-forming assembly which determines the geometric properties of the beam. In addition, it may contain filters to modify the energy spectrum or to reduce the gamma ray content of the beam. The optimum thickness of filters, the position of the aperture and other details of the neutron collimator were calculated using MCNP Monte Carlo simulations. In this design, the L/D ratio of this facility had the value of 120. The thermal neutron flux at the image plane was about 7.8×106 n/cm2.s and n/γ ratio about 106 n/cm2.μSv.

Neutron Based Imaging and Element-mapping at the Budapest Neutron Centre

The Budapest Neutron Centre (BNC) is a consortium of institutes to co-ordinate research activities carried out at the Budapest Research Reactor. It hosts two neutron imaging facilities (RAD and NORMA) operated by the Centre for Energy Research, Hungarian Academy of Sciences and offers access to this scientific infrastructure for the domestic and international users.The radiography station (RAD) at the thermal neutron beamline of the reactor gives a possibility to study relatively large objects by thermal neutron-, gamma- and X-ray radiography, and to benefit from the complementary features of the different radiations. RAD is being extended in 2014 with digital imaging and tomographic capabilities. The image detection is based on suitable converter screens. The static radiography and tomography images are acquired by a new, large area sCMOS camera, whereas the dynamic radiography is accomplished by a low-light-level TV camera and a frame grabber card.The NORMA facility is designed to perform neutron radiography and tomography on small samples using guided cold neutrons. Here two non-destructive techniques are coupled to determine the chemical composition and to visualize the internal structure of heterogeneous objects. The position-sensitive element analysis with prompt-gamma activation analysis (PGAA) and the imaging with neutron radiography/tomography (NR/NT) are integrated into a unique facility called NIPS-NORMA. The goal of such a combination of these methods is to save substantial beam time in the so-called NR/NT-driven PGAI (Prompt Gamma Activation Imaging) mode, in which the interesting regions are first visualized and located, and subsequently the time-consuming prompt-gamma measurements are made only where it is really needed.The paper will give an overview about the technical details of the facilities, and the latest results of selected applications from the fields of archaeometry, engineering and material science.

First Attempts on Energy-selective Neutron Imaging at IBR-2

A new neutron imaging facility has been started at the IBR-2 high flux pulsed reactor. It isattractive not only for traditional neutron imaging applications but in particular also for thedevelopment of modern energy-selective techniques using a time-of-flight methods.A short overview of the first obtained results of theenergy-selected experiments by means of time-of-flight methods realised on neutron radiography and tomography station on high-flux pulsed reactor IBR-2 are presented.

Neutron Imaging Facility Development and Research Trend at NIST

The National Institute of Standards and Technology (NIST)maintains a sustained focus in the development of advanced neutron imaging facilities and hardware components to enable breakthrough research with vastly improved spatial and temporal resolutions, and to identify and employ research practices important to a wide variety of industrial and scientific applications. NIST's main focus is to enable research with broad appeal and commercial impacts. In this article we will give a brief overview of the NIST facility, select examples of current research, and finally comment on emerging technologies including advance manufacturing where neutron imaging has the potential to play an important role.

Design and Characterization of a Hydride-based Hydrogen Storage Container for Neutron Imaging Studies

We have designed, constructed and tested a prototype hydride-based container to in-situ observe the hydride decomposition process using a neutron imaging facility. This work describes the container design parameters and the experimental setup used for the studies. The results open new possibilities for the application of the neutron imaging technique to visualize the internal state of massive hydride-based hydrogen containers, thus aiding in the design of efficient hydrogen storage tanks.

Thermal Neutron Tomography for Cultural Heritage at INR

The neutron and gamma imaging facility placed at the tangential channel of the TRIGA-ACPR from INR was used for tomography investigations on a test object with good results and shortly followed its involvement for tomography investigations on prehistoric statues of clay from the Arges County Museum. This activity was performed in connection with a research contract with IAEA with title “The neutron and gamma imaging method combined with neutron-based analytical methods for cultural heritage research”, in the frame of a current CRP, that helps curators to reveal the internal structure and composition of the objects. The detector system has been developed based on two interchangeable scintillators, one for thermal neutrons and the other one for gamma radiations, a mirror of float glass coated with aluminum and two interchangeable CCD cameras. Experiments of tomography imaging for two prehistoric statues of clay with CCD STARLIGHT XPRESS SXV-H9 camera with XD-4 type image intensifier are presented in this paper. The tomography reconstructions with Octopus software have shown the potential of good results even for 100 projections/1800. This was a good opportunity for the dissemination of the investigation methods based on neutrons for cultural heritage and beyond this area.

Non-destructive Investigation of “The Violinist” a Lead Sculpture by Pablo Gargallo, Using the Neutron Imaging Facility NEUTRA in the Paul Scherrer Institute

The Violinist (1920), the only sculpture made by Gargallo using lead sheet and wood, is being corroded by carbonation, most probably due to the organic vapours released by the wood inside, a material not chemically compatible with lead. Hydrogen plasma has been tested and proved to be an effective treatment meaning that the sculpture has to be dismantled in order to give the plasma gas access to the lead carbonate crusts on the inner surface of the lead sheet. Prior to dismantling, a complete exploration and diagnosis of this lead sculpture has been carried out through neutron imaging at the Paul Scherrer Institute. This non-destructive technique has produced different sets of images including radiography, tomography and 3D reconstruction. Despite the presence of a core made of an organic material such as wood, the digital processing of the images and their in depth visual analysis have yielded new three-dimensional information of inaccessible details of the sculpture, allowing us to assess its present state of conservation and the manufacturing technique and materials used by the artist. The results presented in this article highlight how information from neutron imaging can be of great value when it comes to set the strategies for future conservation treatment

Present and Future Activities on Neutron Imaging in Argentina

We present here a short review of the main work which has been done in the latest years in neutron imaging in Argentina, and the future plans for the development of this technique in the country, mainly focused in the design of a new neutron imaging instrument to be installed in the future research reactor RA10. We present here the results of the implementation of the technique in samples belonging to the Argentinean cultural heritage and experiments related with hydrogen storage. At the same time, the Argentinean RA10 project for the design and construction of a 30 MW multipurpose research reactor is rapidly progressing. It started to be designed by the National Atomic Energy Commission (CNEA) and the technology company INVAP SE, both from Argentina, in June 2010. The construction will start in the beginning of 2015 in the Ezeiza Atomic Center, at 36km from Buenos Aires City, and is expected to be finished by 2020. One of the main aims of the project is to offer to the Argentinean scientific and technology system new capabilities based on neutron techniques. We present here the conceptual design of a neutron imaging facility which will use one of the cold neutron beams, and will be installed in the reactor hall. Preliminary simulation results show that at the farthest detection position, at about 17 m from the cold source, a uniform neutron beam on a detection screen with an intensity of about 108 n/cm2/s is expected.

Overview of the Conceptual Design of the Future VENUS Neutron Imaging Beam Line at the Spallation Neutron Source

VENUS (Versatile Neutron Imaging Beam line at the Spallation Neutron Source) will be a world-class neutron-imaging instrument that will uniquely utilize the Spallation Neutron Source (SNS) time-of-flight (TOF) capabilities to measure and characterize objects across several length scales (mm to μm). When completed, VENUS will provide academia, industry and government laboratories with the opportunity to advance scientific research in areas such as energy, materials, additive manufacturing, geosciences, transportation, engineering, plant physiology, biology, etc. It is anticipated that a good portion of the VENUS user community will have a strong engineering/industrial research focus. Installed at Beam line 10 (BL10), VENUS will be a 25-m neutron imaging facility with the capability to fully illuminate (i.e., umbra illumination) a 20cm x 20cm detector area. The design allows for a 28cm x 28cm field of view when using the penumbra to 80% of the full illumination flux. A sample position at 20 m will be implemented for magnification measurements. The optical components are comprised of a series of selected apertures, T0 and bandwidth choppers, beam scrapers, a fast shutter to limit sample activation, and flight tubes filled with Helium. Techniques such as energy selective, Bragg edge and epithermal imaging will be available at VENUS.

High resolution neutron imaging capabilities at BOA beamline at Paul Scherrer Institut

The cold neutron spectrum of the Beamline for neutron Optics and other Applications (BOA) at Paul Scherrer Institut enables high contrast neutron imaging because neutron cross sections for many materials increase with neutron wavelength. However, for many neutron imaging applications, spatial resolution can be as important as contrast. In this paper the neutron transmission imaging capabilities of an MCP/Timepix detector installed at the BOA beamline are presented, demonstrating the possibilities for studying sub-20µm features in various samples. In addition to conventional neutron radiography and microtomography, the high degree of neutron polarization at the BOA beamline can be very attractive for imaging of magnetic fields, as demonstrated by our measurements. We also show that a collimated cold neutron beamline combined with a high resolution detector can produce image artifacts, (e.g. edge enhancements) due to neutron refraction and scattering. The results of our experiments indicate that the BOA beamline is a valuable addition to neutron imaging facilities, providing improved and sometimes unique capabilities for non-destructive studies with cold neutrons.

Comparison of Water Transport Mechanisms Between Commercial and Experimental Virgin and Aged Diffusion Media Using High Resolution Neutron Radiography

The motivation of this work is to characterize water transport for a new high tortuosity anode diffusion media (DM) and to provide the modeling community with valuable benchmark validation data. The high resolution neutron images in this work were taken at the Neutron Imaging Facility at the National Institute of Standards and Technology (NIST) Center for Neutron Research. Tests were conducted with well-defined boundary conditions and publically available materials. Gradients in pressure, inlet relative humidity, and temperature were used to isolate hydraulic, diffusion, and temperature driven flow through the membrane and porous media.A custom designed 4.8 cm2fuel cell with liquid coolant for precise thermal boundary conditions was used to acquire the neutron images. Test conditions were selected to produce extreme gradients within the cell to push model prediction capabilities. The high resolution neutron images allow for the determination of through-plane water profiles and water transfer rates as a function of current density as shown in Figure 1. Additionally, real-time water balance and net water drag measurements were made with dew point sensors.This talk will discuss the differences in performance and water content of the experimental DM and baseline commercial DM presented previously, and attempt to draw conclusions relating the structural properties of the porous media and resulting performance and water transport and distribution. Additionally, partially degraded materials (e.g. electrodes used for hundreds of hours) will be compared to virgin materials to understand the impact of age and lifetime on water transport and performance. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EREE supported program. Acknowledgements This work is funded by the United States Department of Energy Efficiency and Renewable Energy (EREE) Program through General Motors under Award Number DE-EE0000470. The authors would like to thank Dr. Dan Hussy and Dr. David Jacobson of NIST for their guidance.Figure 1: Liquid water profiles for all 1.5 A/cm2 test conditions for baseline DM (upper) and high tortuosity DM (lower). The high tortuosity DM significantly reduces anode water content for identical operating conditions to baseline.

Trouble Shooting of Deuteron RFQ for PKUNIFTY

A 201.5MHz deuteron four-rod RFQ was designed and operated to generate high flux neutron for the application of neutron radiography at Peking University, which is called as Peking University Neutron Imaging Facility (PKUNIFTY). This paper presents two kinds of tuners to tune the cavity to the designed frequency and reach the needed field unflatness distribution less than 5%; the RFQ intervane voltage 70.7kV determination by the roentgen spectrum measurement at 237.6kW; output accelerated deuteron beam energy at 2.0 MeV with energy spread of 2.5% at 300kW including additional about 60kW beam power. Although it has been running more than one year, sometimes we have troubles not only for the RFQ, mainly for the RF system. This paper showed some troubles and its shootings methods. Some troubles and shooting methods might be useful for similar projects.

Design of Moderator of a Compact Accelerator-driven Neutron Source for Coded Source Imaging

Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux and L/D ratio. Peking University neutron imaging facility (PKUNIFTY) is a RFQ accelerator based facility. The CSI experiments were carried out on PKUNFTY to test the benefits that this technique might bring. The CSI technique gets more restricts on the moderator, especially the neutron distribution in the inner collimator, where the coded mask sampling the source. The effect caused by the non-uniformity of neutron distribution on the mask plane was investigated. The slope type non-uniformity should less than 20% to keep the artifact in the reconstructed image insignificant. The PKUNIFTY moderator was modified according to the above limit. The preliminary experiments shown the moderator design for coded source imaging is acceptable.

Handling radiation generated during an ion source commissioning

Radiation is an important issue, which should be carefully treated during the design and commissioning of an ion source. Measurements show that X-rays are generated around the ceramics column of an extraction system when the source is powered up to 30 kV. The X-ray dose increases greatly when a beam is extracted. Inserting the ceramic column into a metal vacuum box is a good way to block X-ray emission for those cases. Moreover, this makes the online test of an intense H(+) ion beam with energy up to 100 keV possible. However, for deuteron ion source commissioning, neutron and gamma-ray radiation become a serious topic. In this paper, we will describe the design of the extraction system and the radiation doses of neutrons and gamma-rays measured at different D(+) beam energy during our 2.45 GHz deuteron electron cyclotron resonance ion source commissioning for PKUNIFTY (PeKing University Neutron Imaging FaciliTY) project at Peking University.

Design, Construction, and Demonstration of the Colorado School of Mines Neutron Imaging Facility

The MInes NEutron Radiography facility (MINER facility) installed at the United States Geological Survey TRIGA Reactor provides new capabilities for both researchers and students at the Colorado School of Mines. The facility consists of a number of components, including a neutron beamline and beamstop, an optical table, an experimental enclosure and associated interlocks, a computer control system, a microchannel plate imaging detector, and the associated electronics.Radiographs of a sensitivity indicator–a resolution indicator developed by the American Society for Testing and Materials–taken using both the digital detector and the transfer method provide one demonstration of the radiographic capabilities of the new facility. Calibration fuel pins manufactured using copper and stainless steel surrogate fuel pellets provide additional specimens for demonstration of the new facility and offer a comparison between digital and film radiography at the new facility. The calibration pins contain simulated defects of known dimensions, including pellet-clad gaps, gaps between pellets, and central voids within the pellets. Comparison of the radiographs taken by the two methods reveals that the digital detector does not produce high-quality images when compared to film radiography. Additionally, there are a number of artifacts in the digital images produced by the image acquisition system. The quality of the film images demonstrates that the problems with the digital images are a product of the digital imaging system and not the neutron beam.

Commissioning and operation of the deuteron injector for PKUNIFTY project

PKUNIFTY (PeKing University Neutron Imaging FaciliTY), a thermal neutron imaging facility based on a 2 MeV RFQ accelerator, has been constructed at Peking University. Its deuteron injector, which consists of a 2.45 GHz permanent magnet electron cyclotron resonance (PMECR) deuteron ion source and a two-solenoid low energy beam transport (LEBT), aims at producing and delivering 50 mA, 50 keV deuteron beam with a duty factor of 10% (1 ms, 100 Hz). In the preliminary tests of RFQ accelerator, the ECR ion source and LEBT are required to operate at various duty factors (from 1% to 10%). The deuteron ion source has been tested with different pulse widths for this reason. In order to optimize the transmission parameters, the beam current at the exit of RFQ as a function of solenoids tuning and steering magnets tuning are carefully studied. The beam emittance at the entrance of RFQ has been measured with space charge compensation by different argon gas (RG) pressure from 1.6 × 10(-4) Pa to 4.7 × 10(-3) Pa. The measuring results show the best compensating pressure is 3.5 × 10(-3) Pa with a minimal normalized rms emittance of 0.12 pi mm mrad. During the commissioning, we found the purity of deuteron gas is an important factor which severely affects ECR discharge and plasma intensity inside the ion source chamber. The detailed experimental results obtained during the commissioning are discussed in this paper.

Neutron Tomography of a Fuel Cell: Statistical Learning Implementation of a Penalized Likelihood Method

At the NIST Neutron Imaging Facility, we collect neutron projection data for both the dry and wet states of a Proton-Exchange-Membrane (PEM) fuel cell. Transmitted thermal neutrons captured in a scintillator doped with lithium-6 produce scintillation light that is detected by an amorphous silicon detector. Based on joint analysis of the dry and wet state projection data, we reconstruct a residual neutron attenuation image with a Penalized Likelihood method with an edge-preserving Huber penalty function that has two parameters that control how well jumps in the reconstruction are preserved and how well noisy fluctuations are smoothed out. The choice of these parameters greatly influences the resulting reconstruction. We present a data-driven method that objectively selects these parameters, and study its performance for both simulated and experimental data. Before reconstruction, we transform the projection data so that the variance-to-mean ratio is approximately one. For both simulated and measured projection data, the Penalized Likelihood method reconstruction is visually sharper than a reconstruction yielded by a standard Filtered Back Projection method. In an idealized simulation experiment, we demonstrate that the cross validation procedure selects regularization parameters that yield a reconstruction that is nearly optimal according to a root-mean-square prediction error criterion.