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Brookhaven National Laboratory (New York) launched its high-energy X-ray science program at the inception of the National Synchrotron Light Source (NSLS), a U.S. Department of Energy (DOE) Office o...

We report the transformation of an amorphous mixture of Li0.5La0.5TiO3 (LLTO) directly into a single phase dense polycrystal, all within a few seconds at about 800 °C by the flash method. The starting material is a chemically-prepared precursor powder that experiences concurrent crystallization and densification to cubic LLTO during the flash event, as shown by in-situ X-ray measurements. The experiments were conducted at a constant heating rate with fields from 80 to 120 V cm−1 and a current limit of 60 mA mm–2. The resulting polycrystal yielded a bulk conductivity of 0.5 mS cm–1.

Germanium has been the material of choice in detectors of high-energy X-rays and gamma rays for many years, largely because it is relatively easy to obtain high-quality material in large quantities...

The in situ response of stoichiometric and non-stoichiometric uranium dioxide during flash sintering is examined using high energy X-ray diffraction. Our results show that the onset of flash is driven by an increase in temperature and controlled by the applied field with no evidence of an accumulation of defects. The incubation time, that is the time after the application of the field before the flash occurs, is found to be material specific with hyper-stoichiometric samples requiring lower fields to flash. For low current/voltage fields we quantify very little change in the atomic and microstructure of the different uranium dioxide samples post-flash. Microstructural changes are identified for high fields and currents, where joule heating and sample temperatures are high, resulting in the complete transformation of the U4O9 phase. Our results highlight the usefulness of high energy X-ray characterization in understanding the subtle structural changes that occur during the flash sintering process.

The lack of a mechanistic framework for chemical reactions forming inorganic extended solids presents a challenge to accelerated materials discovery. We demonstrate here a combined computational and experimental methodology to tackle this problem, in which in situ X-ray diffraction measurements monitor solid-state reactions and deduce reaction pathways, while theoretical computations rationalize reaction energetics. The method has been applied to the La2CuO4-x S x (0 ≤ x ≤ 4) quaternary system, following an earlier prediction that enhanced superconductivity could be found in these new lanthanum copper(II) oxysulfide compounds. In situ diffraction measurements show that reactants containing Cu(II) and S(2-) ions undergo redox reactions, leaving their ions in oxidation states that are incompatible with forming the desired new compounds. Computations of the reaction energies confirm that the observed synthetic pathways are indeed favored over those that would hypothetically form the suggested compounds. The consistency between computation and experiment in the La2CuO4-x S x system suggests a role for predictive theory: to identify and to explicate new synthetic routes for forming predicted compounds.

The X-ray Powder Diffraction (XPD) Beamline at the National Synchrotron Light Source-II is a multipurpose instrument designed for high-resolution, high-energy X-ray scattering techniques. In this article, the capabilities, opportunities and recent developments in the characterization of radioactive materials at XPD are described. The overarching goal of this work is to provide researchers access to advanced synchrotron techniques suited to the structural characterization of materials for advanced nuclear energy systems. XPD is a new beamline providing high photon flux for X-ray Diffraction, Pair Distribution Function analysis and Small Angle X-ray Scattering. The infrastructure and software described here extend the existing capabilities at XPD to accommodate radioactive materials. Such techniques will contribute crucial information to the characterization and quantification of advanced materials for nuclear energy applications. We describe the automated radioactive sample collection capabilities and recent X-ray Diffraction and Small Angle X-ray Scattering results from neutron irradiated reactor pressure vessel steels and oxide dispersion strengthened steels.

The microstructural response of neutron irradiated 3C-SiC have been investigated over a wide irradiation temperature and fluence range via qualitative and quantitative synchrotron-based X-ray diffraction characterization. We identify several neutron fluence- and irradiation temperature-dependent changes in the microstructure, and directly highlight the specific defects introduced through the course of irradiation. By quantifying the microstructure, we aim to develop a more detailed understanding of the radiation response of SiC. Such studies are important to build mechanistic models of material performance and to understand the susceptibility of various microstructures to radiation damage for advanced energy applications.

We discuss the Arrhenius behavior of electrical conductivity σ during flash sintering of 3 mol% yttria stabilized zirconia (3YSZ). In situ x-ray diffraction is used to determine sample temperature. Sintering contribution to σ is excluded by investigating the flash event on a dense ceramic. We show that total conductivity follows an Arrhenius-like equation in both dense and green samples, even during Stage II of flash. The non-linearity often verified during flash sintering of 3YSZ is therefore related to the furnace temperature instead of the sample temperature when building the ln(σ) vs. 1/T plots. Furthermore, we verified a change in the activation energy for conduction prior to the ignition of the flash event and discussed the possible mechanisms. For instance, the decrease in activation energy from Stage I to II in the dense sample is attributed to a contribution from electronic carriers.

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) has prompted the investigation of novel materials for beam-intercepting devices, and in particular for the collimators responsible for protecting the machine from beam losses. The HL-LHC collimation system will inevitably experience increased levels of radiation damage and undergo changes in their crucial physio-mechanical properties. Graphite-matrix composite materials containing molybdenum carbide particles, along with small amounts of titanium carbide, were developed with the objective of enhanced in-beam performance and tested under proton irradiation. The physical degradation observed in early grades of molybdenum carbide compounds, even after modest proton fluences, has prompted the development of advanced compounds. In this work, we examine the effects of proton irradiation on the microstructural and thermophysical properties of new grades of Molybdenum-carbide-graphite compounds up to fluences of ~2 × 1020 p/cm2. We employ a combination of precision dilatometry and high-energy X-ray diffraction to quantify the dimensional stability and crystallographic phase evolution both pre- and post-irradiation. Our results reveal that these new compounds exhibit superior resilience to radiation damage than their predecessors.

The microstructural response of neutron irradiated 3C-SiC have been investigated over a wide irradiation temperature and fluence range via qualitative and quantitative synchrotron-based X-ray diffraction characterization. We identify several neutron fluence- and irradiation temperature-dependent changes in the microstructure, and directly highlight the specific defects introduced through the course of irradiation. By quantifying the microstructure, we aim to develop a more detailed understanding of the radiation response of SiC. Such studies are important to build mechanistic models of material performance and to understand the susceptibility of various microstructures to radiation damage for advanced energy applications.

WOS: 000401127300016, The study revealed that loss of ductility in an amorphous Fe-alloy coating on a steel substrate composite structure was essentially prevented from occurring, following radiation with modest neutron doses of similar to 2 x 10(18) n/cm(2). At the higher neutron dose of similar to 2 x 10(19), macroscopic stress-strain analysis showed that the amorphous Fe-alloy nanostructured coating, while still amorphous, experienced radiation-induced embrittlement, no longer offering protection against ductility loss in the coating-substrate composite structure. Neutron irradiation in a corrosive environment revealed exemplary oxidation/corrosion resistance of the amorphous Fe-alloy coating, which is attributed to the formation of the Fe2B phase in the coating. To establish the impact of elevated temperatures on the amorphous-to-crystalline transition in the amorphous Fe-alloy, electron microscopy was carried out which confirmed the radiation-induced suppression of crystallization in the amorphous Fe-alloy nanostructured coating. (C) 2017 Published by Elsevier B.V., DOE-NE grant [CT-13BN040505]; U.S. DOE Office of Science FacilityUnited States Department of Energy (DOE) [DE-SC-0012704]; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-SC-0012704, DE-AC02-98CH10886], This research was supported by a DOE-NE grant CT-13BN040505. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC-0012704. This research used resources at XPD beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC-0012704. This research used resources at X17B1 beamline of the National Synchrotron Light Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-AC02-98CH10886.

In hybrid improper ferroelectric systems, polarization arises from the onset of successive nonpolar lattice modes. In this work, measurements and modeling were performed to determine the spatial symmetries of the phases involved in the transitions to these modes. Structural and optical measurements reveal that the tilt and rotation distortions of the $\mathrm{Mn}{\mathrm{O}}_{6}$ or $\mathrm{Ti}{\mathrm{O}}_{6}$ polyhedra relative to the high symmetry phases driving ferroelectricity in the hybrid improper $\mathrm{C}{\mathrm{a}}_{3}{X}_{2}{\mathrm{O}}_{7}$ system $(X=\mathrm{Mn}$ and Ti) condense at different temperatures. The tilt angle vanishes abruptly at ${T}_{\mathrm{T}}\ensuremath{\sim}400$ K for $\mathrm{C}{\mathrm{a}}_{3}\mathrm{M}{\mathrm{n}}_{2}{\mathrm{O}}_{7}$ (and continuously for $X=\mathrm{Ti})$ and the rotation mode amplitude is suppressed at much higher temperatures ${T}_{\mathrm{R}}\ensuremath{\sim}1060$ K. Moreover, Raman measurements in $\mathrm{C}{\mathrm{a}}_{3}\mathrm{M}{\mathrm{n}}_{2}{\mathrm{O}}_{7}$ under isotropic pressure reveal that the polyhedral tilts can be suppressed by very low pressures (between 1.4 and 2.3 GPa) indicating their softness. These results indicate that the $\mathrm{C}{\mathrm{a}}_{3}\mathrm{M}{\mathrm{n}}_{2}{\mathrm{O}}_{7}$ system provides a platform for strain engineering of ferroelectric properties in film-based systems with substrate-induced strain.

The NT-02 neutrino physics target made of the isotropic graphite grade produced neutrinos for the MINOS and MINERVA high-energy physics experiments. The segmented, 95-cm-long NT-02 target was bombarded with a 340 kW, Gaussian 1.1 mm sigma beam of 120 GeV protons reaching $6.516\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target and a peak fluence of $8.6\ifmmode\times\else\texttimes\fi{}{10}^{21}\text{ }\text{ }\mathrm{protons}/{\mathrm{cm}}^{2}$. Reductions in detected neutrino events during the experiment were attributed to radiation-induced damage on the target material leading to the NT-02 target replacement. With future neutrino physics targets aiming at the multimegawatt power regime, identifying life expectancy or fluence thresholds of target materials is of paramount importance, and, therefore, pinpointing the exact cause and target failure mode triggering the neutrino yield reduction is critical. To help unravel the effects of the 120 GeV beam on the isotropic graphite structure at the microstructural or lattice level, x-ray beams from National Synchrotron Light Source II were utilized to study failed in-beam as well as intact NT-02 target segments. The primary objective was to arrive at a scientifically sound explanation of the processes responsible for the target failure by correlating macroscopic observations with microstructural analyses. Results from transmission electron microscopy studies were integrated in assessing the microstructural evolution. The x-ray diffraction study revealed (a) the diffused state reached by the graphite microstructure within the $1\ensuremath{\sigma}$ of the beam where the graphite lattice structure transforms into a nanocrystalline structure, a finding supported by electron microscopy examination, thus providing an indication of the fluence threshold, and (b) the dominant role of the irradiation temperature profile exhibiting a high gradient from the beam center to the heat sink and aggravating the damage induced in the microstructure by the high proton fluence. The effects of the 120 GeV protons on the isotropic graphite target structure are corroborated by observed damage induced by 160-MeV protons and by fast neutrons to comparative doses on similar graphite, an assessment that will aid the design of next-generation megawatt-class neutrino targets.

AlBeMet 162 (Materion Co., formerly Brush Wellman) has been irradiated with 145 MeV protons up to 1.2 × 1020 cm−2 fluence, with irradiation temperatures in the range of 100–220 °C. Macroscopic post-irradiation evaluation on the evolution of mechanical and thermal properties was integrated with a comprehensive X-ray- diffraction study using high-energy monochromatic and polychromatic X-ray beams, which offered a microscopic view of the irradiation damage effects on AlBeMet. The study confirmed the stability of the metal–matrix composite, its resistance to proton damage, and the continuing separation of the two distinct phases, fcc aluminum and hcp beryllium, following irradiation. Furthermore, based on the absence of inter-planar distance change during proton irradiation, it was confirmed that the stacking faults and clusters on the Al (1 1 1) planes are stable, and thus can migrate from the cascade region and be absorbed at various sinks. XRD analysis of the unirradiated AlBeMet 162 showed clear change in the texture of the fcc phase with orientation especially in the Al (1 1 1) reflection which exhibits a “non-perfect” six-fold symmetry, implying lack of isotropy in the composite.

S 200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 10 20 cm −2 peak fluence and irradiation temperatures in the range of 100–200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objective was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4 He and 3 H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. The study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.

Massive, thick-walled pressure vessels are permanent nuclear reactor structures that are exposed to a damaging flux of neutrons from the adjacent core. The neutrons cause embrittlement of the vessel steel that grows with dose (fluence), as manifested by an increasing ductile-to-brittle fracture transition temperature. Extending reactor life requires demonstrating that large safety margins against brittle fracture are maintained at the higher neutron fluence associated with beyond 60 years of service. Here synchrotron-based x-ray diffraction and small angle x-ray scattering measurements are used to characterize highly embrittling nm-scale Mn–Ni–Si precipitates that develop in the irradiated steels at high fluence. These precipitates lead to severe embrittlement that is not accounted for in current regulatory models. Application of the complementary techniques has, for the very first time, successfully identified the crystal structures of the nanoprecipitates, while also yielding self-consistent compositions, volume fractions and size distributions.

IG-430, a fine-grained, isotropic graphite grade is a promising candidate for the future Very High Temperature Reactors (VHTR). IG-430 which provides higher density, strength, and thermal conductivity, has already been developed as a graphite for next-generation HTGR, and is expected to be employed. This graphite grade, however, is lacking enough database that is needed for design. The present study aims to enhance the database with experimental data focusing on the low temperature regime (90–210 °C) by using 120–200 MeV protons to irradiate the IG-430 graphite to peak fluence of ~1.2 1025 m−2. It is anticipated that radiation-induced changes in the graphite properties and damage to be more pronounced in this low temperature regime than in elevated temperatures where damage annealing is taking place simultaneously. IG-430 graphite was characterized following irradiation for mechanical property changes (modulus and strength), dimensional stability and irradiation-induced growth as well as microstructural changes using high energy X-rays and different X-ray diffraction techniques. In assessing proton irradiation effects on the IG-430 graphite grade, comparison of radiation effects was made with the IG-43 grade, the un-purified version of IG-430, as well as other isotropic graphite grades. IG-430 was shown in this study to be better graphitized than other isotropic graphite grades. The study also revealed that during proton irradiation at low temperatures (~100 °C) the IG-430 exhibits stored energy release.

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory's (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.

PURPOSE: Turbid (powder or columnar-structured) scintillators are widely used in indirect flat panel detectors (I-FPDs) for scientific, industrial and medical radiography. Light diffusion and absorption within these scintillators is expected to cause depth-dependent variations in their x-ray conversion gain and spatial blur. These variations degrade the detective quantum efficiency of I-FPDs at all spatial frequencies. Despite their importance, there are currently no established methods for directly measuring scintillator depth effects. This work develops the instrumentation and methods to achieve this capability. METHODS: An ultra-high-sensitivity camera was assembled for imaging single x-ray interactions in two commercial Gd(2)O(2)S:Tb (GOS) screens (Lanex Regular and Fast Back, Eastman Kodak Company). X-ray interactions were localized to known depths in the screens using a slit beam of parallel synchrotron radiation (32 keV), with beam width (~20 µm) much narrower than the screen thickness. Depth-localized x-ray interaction images were acquired in 30 µm depth-intervals, and analyzed to measure each scintillator’s depth-dependent average gain [Formula: see text] and modulation transfer function MTF(z,f). These measurements were used to calculate each screen’s expected MTF(f) in an energy-integrating detector (e.g. I-FPD). Calculations were compared to presampling MTF measurements made by coupling each screen to a high-resolution CMOS image sensor (48 μm pixel) and using the slanted-edge method. RESULTS: Both [Formula: see text] and MTF(z,f) continuously increased as interactions occurred closer to each screen’s sensor-coupled surface. The Regular yielded 1351 ± 66 and 2117 ± 54 photons per absorbed x-ray (42-66 keV(−1)) in interactions occurring furthest from and nearest to the image sensor, while the Fast Back yielded 833 ± 22 and 1910 ± 39 photons (26-60 keV(−1)). At f = 1 mm(−1), MTF(z,f) varied between 0.63-0.78 in the Regular and 0.30-0.76 in the Fast Back. Calculations of presampling MTF(f) using [Formula: see text] and MTF(z,f) showed excellent agreement with slanted-edge measurements. CONCLUSIONS: The developed instrument and method enable direct measurements of the depth-dependent gain and spatial resolution of turbid scintillators. This knowledge can be used to predict, understand, and potentially improve I-FPD imaging performance.

We have developed a series of monolithic multi-element germanium detectors, based on sensor arrays produced by the Forschungzentrum Julich, and on Application-specific integrated circuits (ASICs) developed at Brookhaven. Devices have been made with element counts ranging from 64 to 384. These detectors are being used at NSLS-II and APS for a range of diffraction experiments, both monochromatic and energy-dispersive. Compact and powerful readout systems have been developed, based on the new generation of FPGA system-on-chip devices, which provide closely coupled multi-core processors embedded in large gate arrays. We will discuss the technical details of the systems, and present some of the results from them., 10 pages, 14 figures, Accepted J. Instrumentation

We report here a course of basic research into the potential suitability of a pseudo-icosahedral Cr aluminide as a material for high-temperature protective coatings. ${\mathrm{Cr}}_{55}{\mathrm{Al}}_{232\ensuremath{-}\ensuremath{\delta}}\phantom{\rule{4pt}{0ex}}\mathrm{[}\ensuremath{\delta}=2.70(6)]$ exhibits high hardness at room temperature as well as low thermal conductivity and excellent oxidation resistance at 973 K, with an oxidation rate comparable to those of softer, denser benchmark materials. The origin of these promising properties can be traced to competing long-range and short-range symmetries within the pseudo-icosahedral crystal structure, suggesting new criteria for future materials research.

A comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage., Comment: 20 pp

We have employed x-ray total scattering to investigate the structure of polycrystalline 3C-silicon carbide following neutron irradiation. The structure as a function of irradiation temperature and dose was quantified by analyzing pair distribution functions. Although the SiC matrix retains its crystal structure after irradiation, a significant increase in the diffuse scattering component is observable indicating that neutron irradiation leads to changes in both the short- and medium-range order. These changes include both an irradiation dose- and temperature-dependent increase in the vacancy concentration leading to an increase in the Si and C atomic displacement parameters. A dose-dependent decrease in the size of defect free material is also quantified from the structural refinements due to an increase in the number of defects and defect clusters. Evidence of additional correlations in the short-range order (up to ∼4 A) from differential pair distribution function analysis indicate that combinations of atomistic defects including anti-site defects, vacancies and defect clusters are present after these irradiation conditions. Such structural information will be valuable for direct comparison of experimental and simulated atomic structures of irradiated silicon carbide.

We report development of micro-focusing optics for high-energy x-rays by combining a sagittally bent Laue crystal monchromator with Kirkpatrick-Baez (K–B) X-ray focusing mirrors. The optical system is able to provide a clean, high-flux X-ray beam suitable for pair distribution function (PDF) measurements at high pressure using a diamond anvil cell (DAC). A focused beam of moderate size (10–15 μm) has been achieved at energies of 66 and 81 keV. PDF data for nanocrystalline platinum (n-Pt) were collected at 12.5 GPa with a single 5 s X-ray exposure, showing that the in-situ compression, decompression and relaxation behavior of samples in the DAC can be investigated with this technique. PDFs of n-Pt and nano Au (n-Au) under quasi-hydrostatic loading to as high as 71 GPa indicate the existence of substantial reduction of grain or domain size for Pt and Au nanoparticles at pressures below 10 GPa. The coupling of sagittally bent Laue crystals with K–B mirrors provides a useful means to focus high-energy synchrotron X-rays from a bending magnet or wiggler source.