A Ce-Doped LiI Scintillator Film-Based High Rate, High Spatial Resolution Neutron Anger Camera for Neutron Scattering Facilities

Neutron imaging is one of the key technologies for non-destructive transmission testing. Recent progress in the development of intensive neutron sources allows us to perform energy-resolved neutron imaging with high spatial resolution. Substantial efforts have been devoted to developing a high spatial and temporal resolution neutron imager. We have been developing a neutron imager aiming at conducting high spatial and temporal resolution imaging based on a delay-line neutron detector, called the current-biased kinetic-inductance detector, with a conversion layer 10B. The detector allowed us to obtain a neutron transmission image with four signal readout lines. Herein, we expanded the sensor active area, and improved the spatial resolution of the detector. We examined the capability of high spatial resolution neutron imaging over the sensor active area of 15 × 15 mm2 for various samples, including biological and metal ones. We also demonstrated an energy-resolved neutron image in which stainless-steel specimens were discriminating of other specimens with the aid of the Bragg edge transmission.

With the increasing desire for fast charging capabilities in lithium-ion batteries due to the popularity of electric vehicles, research has recently been focused on increasing energy and power density while simultaneously revealing the need for improved safety mechanisms and decreased overall cost. In response to this need, interest in thick battery electrodes has increased. By increasing the active material per unit area within the electrode, the energy density is increased due to minimization of current collectors, separators, and other packaging components. However, increasing the thickness of electrodes introduces new challenges, including charge-transport limitations.To successfully address the desired increase of energy density and capability of fast charging, high spatial resolution in operando neutron radiography (nR) was utilized to better understand the correlation between microstructure and lithium transport of ultra-thick electrodes. This allows for a comparison between the electrochemical processes occurring during cycling and what is seen in neutron imaging, bridging the gap between microstructural observation and electrochemical testing. Two differing fabrication methods were used to prepare the cathodes and anodes: a solvent free method using a hydraulic press and a wet cast method using N-methyl-pyrrolidone solvent (NMP). The fabrication methods were purposefully chosen to yield differing electrode microstructures. The lithium-ion batteries used in this work were fabricated using graphite (graphite (90 wt%): carbon black (5 wt%): polyvinylidene fluoride (5 wt%)) anodes and NMC (Li(Ni0.8Mn0.1Co0.1)O2) (80 wt%): carbon black (10 wt%): polyvinylidene fluoride (10 wt%)) cathodes with a thickness of ~2.5mm and diameter of 10mm. A deuterated electrolyte (1M LiPF6 EC/DMC=30/70 (v/v)) was used in order to improve the attenuation of lithium within the electrodes. Custom cells were fabricated using PFA Swagelok components to avoid any unnecessary neutron attenuation during neutron radiography. High-resolution (7.5 µm pixel size) in operando nR was performed on these cells using the Multimodal Advanced Radiography Station (MARS) beamline at the Oak National Laboratory High Flux Isotope Reactor. High spatial resolution neutron tomography (nCT) was performed on a cycled battery following in operando nR.Comparing changes in the attenuation coefficient for both a solvent free anode and wet cast anode reveals distinct lithiation patterns in each electrode. In the solvent free sample, there is a dense, but thin, lithium rich region near the separator. In the wet cast sample, the lithium distribution is more evenly dispersed through the thickness of the electrode. The difference in distribution is likely due to the different average pore size of the samples, as represented by the size distribution of macroscopic porosity (pore radius > 20 µm) observed from high resolution nCT. From a comparison of the macroscopic pore radius for each fabrication method it is clear that the solvent free method yields smaller pores and an increased number of pores, whereas the wet cast method yields larger pores and a decreased number of pores. Results from in operando nR during electrochemical cycling and ex situ high spatial resolution nCT on cycled electrodes show that lithium distributions and plating risks are shown to be controlled by both the macroscopic structure of the electrodes and the network of pores and microscale active areas that support electrochemical reactions. This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Special microchannel plates (MCPs) developed by Nova Scientific Inc. incorporate high efficiency neutron conversion materials into the MCP to provide a high neutron stopping power. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nat</sup> Gd have high interaction cross sections for thermal neutrons and their incorporation into MCP glass is a convenient way to make efficient MCPs for neutron detection with high spatial resolution. We have evaluated neutron event counting 2D imaging detectors using these MCPs with a cross delay line readout, cross strip readout, and a Medipix2 readout. Tests at several reactors with the cross delay line and cross strip readouts have established spatial resolution with neutrons as good as ~30 microns FWHM over a 27 mm diameter detector, with event rates approaching 1 MHz, low fixed pattern noise, event time tagging of 25 ns and intrinsic background rates of < 0.05 events cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> sec <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Evaluation of neutron sensing MCP detector with Medipix2 readout (14 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) has allowed operation at high counting rates (500 MHz) with the spatial resolution limited by the 55 micron pixel size of the Medipix2 readout. We have also used the Medipix2 for centroiding of neutron events to sub pixel resolution to obtain better spatial resolution (< 15 mum) for neutrons at reduced event rates (100 kHz). Initial measurements of thermal neutron detection efficiencies give values of 20% to 25% for thermal neutrons and 45% for cold neutrons without optimization of the detection geometry. Preliminary tests with shielding and a LaBr scintillator to gate neutron detections in coincidence with gamma rays produced by neutron interactions has enabled gamma ray rejection factors of 3 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> to be achieved. Further improvements in the neutron detection efficiency and gamma ray discrimination efficiency can be gained by optimization of the geometrical and electronic configurations.

The measurement of the presampled MTF of a high spatial resolution neutron imaging system

The existence of resonance peaks in neutron absorption spectra in the epithermal range of energies enables unique non-destructive testing techniques. The deep penetration of epithermal neutrons provides the opportunity to perform a compositional analysis of a sample which is opaque to X-rays and thermal neutrons. The neutron resonances in the transmission spectra constitute a characteristic pattern for many isotopes, which can be used to identify the isotope and to map the distribution of the isotope in a sample. The neutron transmission spectra can be measured with the time of flight (TOF) technique using a pulsed neutron source. Combining this method with a high resolution neutron counting detector enables substantial improvements of spatial resolution of neutron resonance transmission imaging. Such a detector has been developed to register neutrons with 55 µm spatial and 10–1000 ns temporal resolution Our proof-of-principle experiments at the ISIS pulsed neutron spallation source demonstrate that compositional analysis of multi-element samples can now be performed with ∼150 µm spatial resolution. Images of a test mask consisting of &#60;200 µm thick foils of Au, Ag, In and Gd were collected in the 1–100 eV energy range. The experimental results demonstrate the potential for compositional analysis via resonance absorption transmission with high spatial resolution. In-bulk temperature measurement through Doppler broadening analysis will also benefit from this technique.

Fabrication and experimental evaluation of microstructured 6Li silicate fiber arrays for high spatial resolution neutron imaging

The rapidly developing field of high resolution neutron radiography primarily concentrates on non-destructive studies of stationary objects with relatively long exposure times required to achieve adequate neutron statistics. The combination of a high intensity neutron beam with a high temporal and spatial resolution detector, enables the investigation of dynamic processes in a stroboscopic mode, where image frames are synchronized with the sample or acquired continuously at high acquisition frame rates. Although neutron statistics in the acquisition frames as short as <; 10 μs is considered quite low (typically <; 1000 n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the sample), repetitive processes can still be studied with high resolution by integrating a large number of frames synchronized to the process. In this paper we demonstrate the stroboscopic imaging capabilities of the highly collimated thermal neutron beamline ANTARES together with a high resolution detector with neutron-sensitive microchannel plates and the Medipix2 readout. The dynamics of water uptake due to capillary forces as well as the two-phase flow of an air-water mixture is investigated, and stroboscopic imaging of an operating beam chopper and a spinning fan is performed, with sub-100-μm spatial resolution and with acquisition frames varying between 10 μs and 200 ms. The results of these experiments demonstrate the future potential for performing high resolution neutron radiography of fast and/or repetitive processes, such as water flow and uptake, operation of fuel injection nozzles, as well as many others.

The rapidly developing field of high resolution neutron radiography primarily concentrates on non-destructive studies of stationary objects with relatively long exposure times required to achieve adequate neutron statistics. The combination of a high intensity neutron beam with a high temporal and spatial resolution detector, enables the investigation of dynamic processes in a stroboscopic mode, where image frames are synchronized with the sample or acquired continuously at high acquisition frame rates. Although neutron statistics in the acquisition frames as short as <10 ¿s is considered quite low (typically <1000 n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the sample), repetitive processes can still be studied with high resolution by integrating a large number of frames synchronized to the process. In this paper we demonstrate the stroboscopic imaging capabilities of the highly collimated thermal neutron beamline ANTARES together with a high resolution detector with neutron sensitive microchannel plates and the Medipix2 readout. The dynamics of water uptake due to capillary forces as well as the two-phase flow of an air-water mixture is investigated, and stroboscopic imaging of an operating beam chopper and a spinning fan is performed, with sub-100 ¿m spatial resolution and with acquisition frames varying between 10 ¿s and 200 ms. The results of these experiments demonstrate the future potential for performing high resolution neutron radiography of fast and/or repetitive processes, such as water flow and uptake, operation of fuel injection nozzles, as well as many others.

High resolution neutron counting sensors with microchannel plates coupled to a Timepix readout enable high spatial (~55 μm) and temporal (~1 μs) accuracy for each detected thermal and cold neutron. One of the attractive applications for those sensors is the high resolution strain mapping in engineering samples through transmission Bragg edge diffraction. The unique combination of high detection efficiency (up to 70%), high spatial and temporal resolution of MCP detectors enable ~100 μm strain mapping with ~100 μstrain accuracy. We present the results of proof of principle measurements performed at ROTAX beamline at ISIS spallation neutron source. Strain map of a bent steel sample is measured with very high spatial resolution. The same sensors enable high resolution non-destructive studies in such diverse areas as neutron microtomography, dynamics of fuel injection, material composition, archaeology, water propagation and many others.

A significant fraction of the reservoirs across the world as well as in East &amp; West Malaysia consist of thinly bedded deposits in Fluvial, Deltaic, Deep-water sediments and Channel system. It is estimated that approximately 30-40% of hydrocarbon in place resources are deposited in thin laminated reservoirs that typically laminated formation with sand and shale alternate layers. These thinly bedded reservoirs have lots of hydrocarbon potential which cannot be evaluated by conventional logs, thereby causing underestimation of reserves. This paper presents a new technique to unlock hydrocarbon potential reserves in thinly bedded reservoir using an innovative high-resolution technology (HiRes). The workflow consists of two main steps: first, to create HiRes resistivity log from conventional deep resistivity and high resolution (resistivity image) log, and second, to generate high resolution density and neutron log utilizing HiRes resistivity log created in earlier step. Then standard petrophysical workflow to compute porosity and water-saturation can be continued with developed HiRes resistivity, density, and neutron logs. Currently this workflow has been developed on resistivity image logs, such as Oil Based Mud Imager (OBMI) or Oil Mud Reservoir Imager (OMRI) typically run-in wells drilled with oil-based mud. This new technique was then tested in few wells from different offshore fields having different environment of depositions, in the East and West Malaysia basins. The HiRes technology has been tried on many wells in various Malaysian fields. Those wells were selected based on the available complete well-log suite data including its core data. The outcome processed logs were then verified with the core-laboratory analysis results i.e., with routine core analysis (grain density, porosity, permeability), and with Dean Stark analysis for water saturation. The results showed remarkable results thus proving the robustness of the technology. A non-pay is reinterpreted as pay zone using this technology thus enhance the volume estimation. The HiRes technology provides behind casing perforation opportunity as the new zones could be added which were considered as non-pay by conventional methods. Since HiRes method produces high resolution resistivity, density, and neutron curves, and thereby provides better lithology and bed boundary definition. The HiRes, an innovative in-house technology, not only addresses the problem in thin beds but also provides quantitative petrophysical solution of thinly bedded reservoirs which aligns with the core results. Consequently, HiRes certainly improves the accuracy in the geological interpretation and resulting geological model.

The recent developments in scientific complementary metal oxide semiconductor (sCMOS) detector technology allow for imaging of relevant processes with very high temporal resolution with practically negligible readout time. However, it is neutron intensity that limits the high temporal resolution neutron imaging. In order to partially overcome the neutron intensity problem for the high temporal resolution imaging, a parabolic neutron focussing guide was utilized in the test arrangement and placed upstream the detector in such a manner that the focal point of the guide was positioned slightly behind the scintillator screen. In such a test arrangement, the neutron flux can be increased locally by about one order of magnitude, albeit with the reduced spatial resolution due to the increased divergence of the neutron beam. In a pilot test application, an in-situ titration system allowing for a remote delivery of well-defined volumes of liquids onto the sample stage was utilized. The process of droplets of water (H2O) falling into the container filled with heavy water (D2O) and the subsequent process of the interaction and mixing of the two liquids were imaged with temporal resolution of 0.01s.•Combination of neutron focussing device and use of sCMOS detector allows for very high temporal resolution neutron imaging to be achieved (albeit with reduced spatial resolution and field of view).•In-situ neutron imaging titration device for liquid interaction experiments.•Interaction of otherwise indiscernible liquids (H2O and D2O) visualized using neutron radiography with 0.01s temporal resolution.

Direct evidence for B-B contact in amorphous Ni 2B from high-resolution neutron diffraction

Neutron imaging is one of the most powerful tools for nondestructive\ninspection owing to the unique characteristics of neutron beams, such as high\npermeability for many heavy metals, high sensitivity for certain light\nelements, and isotope selectivity owing to a specific nuclear reaction between\nan isotope and neutrons. In this study, we employed a superconducting detector,\ncurrent-biased kinetic-inductance detector (CB-KID) for neutron imaging using a\npulsed neutron source. We employed the delay-line method, and high spatial\nresolution imaging with only four reading channels was achieved. We also\nperformed wavelength-resolved neutron imaging by the time-of-flight method for\nthe pulsed neutron source. We obtained the neutron transmission images of a\nGd-Al alloy sample, inside which single crystals of GdAl3 were grown, using the\ndelay-line CB-KID. Single crystals were well imaged, in both shapes and\ndistributions, throughout the Al-Gd alloy. We identified Gd nuclei via neutron\ntransmissions that exhibited characteristic suppression above the neutron\nwavelength of 0.03 nm. In addition, the ^{155}Gd resonance dip, a dip structure\nof the transmission caused by the nuclear reaction between an isotope and\nneutrons, was observed even when the number of events was summed over a limited\narea of 15 X 12 um^2. Gd selective imaging was performed using the resonance\ndip of ^{155}Gd, and it showed clear Gd distribution even with a limited\nneutron wavelength range of 1 pm.\n

LiF crystals as high spatial resolution neutron imaging detectors

Radiographic imaging of irradiated fuels has routinely been qualitative in nature, providing information on the general condition of internal components of a fuel pin. Conventional X-ray and neutron radiographic techniques, applicable to irradiated fuels, have not been of high enough resolution to be useful for quantitative image analysis. Recently, however, high resolution neutron radiographic techniques and image analysis, using precision micro-densitometry, have been developed at HEDL. The versatility of these radiographic techniques and associated image analysis is such that precision measurements of highly radioactive components can be performed with minimal modification. The use of high resolution neutron radiography and associated image analysis techniques can significantly reduce the cost of fuel pin performance evaluation by decreasing the number of destructive examinations required. This paper describes the development of a high resolution neutron radiographic imaging method, and the modification of a previously developed system to obtain quantitative measurements from neutron radiographs.