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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Thallium-based scintillators for high-resolution gamma-ray spectroscopy: Ce 3+ - doped Tl 2 LaCl 5 and Tl 2 LaBr 5

In this paper we report on the crystallographic and scintillation properties of Tl 2 LaCl 5 :Ce 3 + and Tl 2 LaBr 5 :Ce 3 + , two novel thallium-containing high-resolution scintillators for gamma-ray spectroscopy. Crystals of Tl 2 LaCl 5 :Ce 3 + and Tl 2 LaBr 5 :Ce 3 + were grown by the Vertical Bridgman method up to 1-inch diameter and 1-inch long. Single crystals of Tl 2 LaCl 5 :Ce 3 + and Tl 2 LaBr 5 :Ce 3 + belong to the orthorhombic system with space group 62 and have a density of 5.16 and 5.98 g/cm 3 , respectively. The scintillators show high light yields of up to 68,000 photons/MeV, excellent gamma-ray energy resolution of ≤ 3% at 662 keV, a fast scintillation decay, and a proportional response over a wide range of energies from 32 keV up to 1275 keV. Density Functional Theory calculations show that the Ce 3 + energy levels are inside the bandgap despite the smaller bandgap of Tl 2 LaCl 5 and Tl 2 LaBr 5 compared to K 2 LaCl 5 and K 2 LaBr 5 . Finally, a systematic Ce 3 + concentration study was performed for Tl 2 LaCl 5 :Ce 3 + and trends observed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Polarization splitting with cubic crystals evaluated with synchrotron radiation

X-ray polarization-splitting crystals separate incident x rays into two components with perpendicular polarization by Bragg reflections at 45° from paired sets of internal planes. Here, the polarization-splitting properties of a germanium crystal are verified using incompletely polarized synchrotron radiation. Further, cleaner data would have come from a beam with a higher degree of polarization, which is achievable with small changes in the experimental geometry.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Inference of experimental radial impurity transport on Alcator C-Mod: Bayesian parameter estimation and model selection

We present a fully Bayesian approach for the inference of radial profiles of impurity transport coefficients and compare its results to neoclassical, gyrofluid and gyrokinetic modeling. Using nested sampling, the Bayesian Impurity Transport InferencE (BITE) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power and reliability with respect to previously demonstrated methods. BITE employs a forward model based on the pySTRAHL package, built on the success of the well-known STRAHL code [Dux, IPP Report, 2004], to simulate impurity transport in magnetically-confined plasmas. In this paper, we focus on calcium (Ca, Z=20) Laser Blow-Off injections into Alcator C-Mod plasmas. Multiple Ca atomic lines are diagnosed via high-resolution X-ray Imaging Crystal Spectroscopy and Vacuum Ultra-Violet measurements. We analyze a sawtoothing I-mode discharge for which neoclassical and turbulent (quasilinear and nonlinear) predictions are also obtained. Here, we find good agreement in diffusion across the entire radial extent, while turbulent convection and density profile peaking are estimated to be larger in experiment than suggested by theory. Efforts and challenges associated with the inference of experimental pedestal impurity transport are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Experimental inference of neutral and impurity transport in Alcator C-Mod using high-resolution x-ray and ultra-violet spectra

We present experimental inferences of cross-field impurity transport coefficients for AlcatorC-Mod plasmas without edge-localized modes, leveraging a novel forward model for the entire Ca Kα spectrum, including satellite lines within the spectral range, to compare to high-resolution x-ray imaging crystal spectroscopy (XICS). These measurements are complemented by extreme ultra-violet (EUV) spectroscopy that constrains transport closer to the edge. Using new atomic data sets for both XICS and EUV analysis has enabled consideration of line ratios across both spectral ranges and has increased the accuracy of inferred transport coefficients. Inclusion of charge exchange between edge thermal neutrals and impurities is shown to be extremely important in C-Mod pedestals. Atomic D neutral densities from experimental D Lyα measurements at the midplane are compared to SOLPS-ITER simulations, finding good agreement. Bayesian inferences of impurity transport coefficients are presented for L-, EDA H-, and I-mode discharges, making use of the Aurora package for forward modeling and combining our spectroscopic constraints. Experimentally inferred diffusion profiles are found to match turbulent transport models at midradius within uncertainties, using both quasilinear gyro-fluid TGLF SAT-1 and nonlinear ion-scale gyrokinetic CGYRO simulations. Furthermore, significant discrepancies in convection are observed in some cases, suggesting difficulties in predictions of flat or hollow impurity profiles.

neutrals↗
DOE OSTI2024

Dielectronic satellite emission from a solid-density Mg plasma: Relationship to models of ionization potential depression

Here, we report on experiments where solid-density Mg plasmas are created by heating with the focused output of the Linac Coherent Light Source x-ray free-electron laser. We study the K-shell emission from the helium- and lithium-like ions using Bragg crystal spectroscopy. Observation of the dielectronic satellites in lithium-like ions confirms that the M-shell electrons appear bound for these high charge states. An analysis of the intensity of these satellites indicates that when modeled with an atomic-kinetics code, the ionization potential depression model employed needs to produce depressions for these ions which lie between those predicted by the well known Stewart-Pyatt and Ecker-Kroll models. These results are largely consistent with recent density functional theory calculations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Inference of Experimental Radial Impurity Transport on Alcator C-Mod: Bayesian Parameter Estimation and Model Selection.

We present a fully Bayesian approach for the inference of radial profiles of impurity transport coefficients and compare its results to neoclassical, gyrofluid and gyrokinetic modeling. Using nested sampling, the Bayesian Impurity Transport InferencE (BITE) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power and reliability with respect to previously demonstrated methods. BITE employs a forward model based on the pySTRAHL package, built on the success of the well-known STRAHL code [Dux, IPP Report, 2004], to simulate impurity transport in magnetically-confined plasmas. In this paper, we focus on calcium (Ca, Z=20) Laser Blow-Off injections into Alcator C-Mod plasmas. Multiple Ca atomic lines are diagnosed via high-resolution X-ray Imaging Crystal Spectroscopy and Vacuum Ultra-Violet measurements. We analyze a sawtoothing I-mode discharge for which neoclassical and turbulent (quasilinear and nonlinear) predictions are also obtained. We find good agreement in diffusion across the entire radial extent, while turbulent convection and density profile peaking are estimated to be larger in experiment than suggested by theory. Efforts and challenges associated with the inference of experimental pedestal impurity transport are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Fe 3+ /Fe T ratios of amphiboles determined by high spatial resolution single-crystal synchrotron Mössbauer spectroscopy

The Fe 3+ /Fe T ratios (Fe 3+ /[Fe 2+ +Fe 3+ ]) in minerals can be used to understand their crystallization and post-crystallization conditions. However, as natural minerals are often zoned and contain inclusions, bulk techniques, e.g., wet chemistry, may not provide accurate Fe 3+ /Fe T values for a single phase of interest. We determined Fe 3+ /Fe T ratios of amphiboles in different crystallographic orientations by single-crystal synchrotron Mössbauer spectroscopy (SMS) in energy and time domain modes from four volcanic localities (Long Valley Caldera, Mount St. Helens, Lassen Volcanic Center, U.S.A., and Mt. Pinatubo, Philippines). The high spatial resolution (as low as 12 × 12 μm spot size) and standard-free nature of SMS allow the detection of intra-grain compositional heterogeneities in Fe 3+ /Fe T with relatively low uncertainties. Here, we combine SMS with major element compositions, water contents, and hydrogen isotope compositions to document the Fe 3+ /Fe T ratios as a function of mineral composition and post-crystallization dehydrogenation. Spectra were fitted with up to five distinct sites: ferrous iron on M(1), M(2), M(3), and ferric iron on M(2) and M(3), consistent with X-ray diffraction studies on single crystals of amphibole. The Fe 3+ /Fe T ratios range from 0.14 ± 0.03 (Long Valley Caldera), 0.51 to 0.63 ± 0.02 (representing intra-grain heterogeneities, Mount St. Helens) to 0.86 ± 0.03 (Lassen Volcanic Center). The latter grain experienced post-crystallization dehydrogenation, shown by its low water content (0.6 ± 0.05 wt%) and its elevated hydrogen isotope composition (δD = +25 ± 3‰ relative to SMOW). The Fe 3+ /Fe T ratios of 0.62 ± 0.01 and 0.20 ± 0.01 of two Mt. Pinatubo grains correlate with high-Al 2 O 3 cores and low-Al 2 O 3 rims and smaller phenocrysts in the sample, respectively. This study shows that SMS is capable of distinguishing two different domains with dissimilar Fe 3+ /Fe T values formed under different crystallization conditions, demonstrating that SMS in combination with major element, water, and hydrogen isotope compositions allows the interpretation of amphibole Fe 3+ /Fe T ratios in the context of crystallization and post-crystallization processes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Remote sensing of Pu in uranyl nitrate crystals using reflectance spectroscopy and chemometrics

Remote quantification of Pu(VI) (0–5 mol%) co-crystallized with U in uranyl nitrate hexahydrate (UNH) crystals was achieved in a glove box using reflectance spectroscopy coupled with chemometric modeling. Reflectance spectra were also acquired for Pu(IV) and Np(VI) (0–5 mol%) crystallized with UNH; revealing spectral features consistent with their solution-phase analogs. Principal component analysis revealed Pu(IV/VI) and Np(VI) concentrations as the primary source of variation in the data, informing the development of a supervised partial least squares regression model for Pu(VI). The resulting calibration demonstrated robust performance, with replicate root mean square errors near 10% and quantifiable limits near 0.2 mol% Pu(VI) relative to U. The Pu(VI) remained stable in the crystalline UNH matrix for at least one week with minimal reduction to Pu(IV). Notably, Pu(VI) and Np(VI) incorporation in UNH quenched U(VI) fluorescence while Pu(IV) did not. This study presents a noninvasive, spectroscopic approach for solid-state Pu quantification, with direct implications for material accountability and nuclear nonproliferation monitoring.

Sadergaski, Luke R. [Oak Ridge National Laboratory↗
NASA NTRS1995

Crystal Growth and Spectroscopy of Diglycine

Raman and infrared spectra have been obtained for alpha-diglycine (C4H8N2O3) single crystals. These dipeptide crystals are being grown as a models system for protein crystal growth studies. There have been previous Raman measurements on diglycine powder samples recorded, but there is no reference to measurements on oriented diglycine single crystals. Diglycine can grow in one of three forms, alpha, beta, or gamma.

Taylor, Taravia M.↗
DOE OSTI2024

Identification and Suppression of Point Defects in Bromide Perovskite Single Crystals Enabling Gamma‐Ray Spectroscopy

Abstract Methylammonium lead tribromide (MAPbBr 3 ) stands out as the most easily grown wide‐band‐gap metal halide perovskite. It is a promising semiconductor for room‐temperature gamma‐ray ( γ ‐ray) spectroscopic detectors, but no operational devices are realized. This can be largely attributed to a lack of understanding of point defects and their influence on detector performance. Here, through a combination of crystal growth design and defect characterization, including positron annihilation and impedance spectroscopy, the presence of specific point defects are identified and correlated to detector performance. Methylammonium (MA) vacancies, MA interstitials, and Pb vacancies are identified as the dominant charge‐trapping defects in MAPbBr 3 crystals, while Br vacancies caused doping. The addition of excess MABr reduces the MA and Br defects and so enables the detection of energy‐resolved γ ‐ray spectra using a MAPbBr 3 single‐crystal device. Interestingly, the addition of formamidinium (FA) cations, which converted to methylformamidinium (MFA) cations by reaction with MA + during crystal growth further reduced MA defects. This enabled an energy resolution of 3.9% for the 662 keV 137 Cs line using a low bias of 100 V. The work provides direction toward enabling further improvements in wide‐bandgap perovskite‐based device performance by reducing detrimental defects.

Ni, Zhenyi↗
DOE OSTI2022

Inferring relative dose-dependent color center populations in proton irradiated thoria single crystals using optical spectroscopy

In this work, we have utilized photoluminescence spectroscopy and optical ellipsometry to characterize the dose-dependence of the photoluminescence emission intensity and changes in optical absorption of thoria single crystals subject to irradiation with energetic protons at room- and elevated-temperatures. The photoluminescence peaks and the optical absorption bands are attributed to creation of new electronic states emerging from defects resulting from displacement damage. These bands are most likely associated with electrons trapped at the oxygen vacancy sites similar to color centers formed in other irradiated oxides and halides. Our experimental observations are supported by a standard density functional theory calculation of the electronic structure in pristine and oxygen vacancy-bearing thoria crystals. The dose-dependence of the intensity of the photoluminescence peaks is used to parameterize a rate theory model that estimates the concentration of color centers in the irradiated crystals. This parameterization provides optimized migration barrier parameters for oxygen interstitials and vacancies that simultaneously capture the optical response of the crystals irradiated at room- and elevated-temperature. These optical spectroscopy techniques offer a promising pathway to characterize the population of color centers formed at the sites of oxygen anion vacancies, particularly in irradiated nuclear fuels, where atomic-level defects cannot be readily imaged using electron microscopy. When combined with other direct and indirect characterization tools, our approach can provide new insight into defect formation and accumulation in energy materials over single atomic to extended length scales.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Single crystal structure, vibrational spectroscopy, gas sorption and antimicrobial properties of a new inorganic acidic diphosphates material (NH 4 ) 2 Mg(H 2 P 2 O 7 ) 2 • 2 H 2 O

We report on the successful synthesis of diammonium magnesium dihydrogendiphosphate (V) dihydrate compound (NH 4 ) 2 Mg(H 2 P 2 O 7 ) 2 •2H 2 O using a wet chemical route. Single crystal X-ray diffraction analysis and micro Raman spectroscopy are employed to characterize the compound. We demonstrate, using a multidisciplinary approach, that this compound is ideal for carbon dioxide (CO 2 ) capture in addition to other anthropogenic gasses. We show here -from both an experimental as well as from a density functional theory (DFT) calculations routes- the potential for adopting this compound into domestic air-conditioning units (ACUs). From these experiments, the resistance to bacterial growth is also investigated, which is critical for the adoption of this compound in ACUs. Our compound exhibits a higher methane (CH 4 ) sorptivity as compared to CO 2 at 25 °C and 45 °C under pressures up to 50 bars. Furthermore, DFT electronic structure calculations are used to compute the main structural and electronic properties of the compound, taking into consideration the characteristics of the identified pores as a function of the progressive CO 2 vs. CH 4 loadings. Finally, the antibacterial assay reveals a strong antibacterial activity against the tested Gram-positive and Gram-negative bacteria, with a large zone of inhibition against the tested E. Coli, S. Aureus and K. Pneumonia

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Caught in the H inact : Crystal Structure and Spectroscopy Reveal a Sulfur Bound to the Active Site of an O 2 -stable State of [FeFe] Hydrogenase

[FeFe] hydrogenases are the most active H 2 converting catalysts in nature, but their extreme oxygen sensitivity limits their use in technological applications. The [FeFe] hydrogenases from sulfate reducing bacteria can be purified in an O 2 -stable state called H inact . To date, the structure and mechanism of formation of H inact remain unknown. Our 1.65 Å crystal structure of this state reveals a sulfur ligand bound to the open coordination site. Furthermore, in-depth spectroscopic characterization by X-ray absorption spectroscopy (XAS), nuclear resonance vibrational spectroscopy (NRVS), resonance Raman (RR) spectroscopy and infrared (IR) spectroscopy, together with hybrid quantum mechanical and molecular mechanical (QM/MM) calculations, provide detailed chemical insight into the Hinact state and its mechanism of formation. This may facilitate the design of O 2 -stable hydrogenases and molecular catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1977

Bent crystal spectrometer for solar X-ray spectroscopy

A bent crystal spectrometer employs a collimated beam of X-rays incident on the crystal over a range of Bragg angles determined by the orientation and curvature of the crystal surface. It provides continuous and simultaneous coverage of all X-ray wavelengths within its spectral range. In-flight testing for solar X-ray spectroscopy was performed using a small instrument to supplement the wavelength coverage of several scanning spectrometers used to study solar active regions in the 9-24 A range. Later testing included modifications to alleviate problems caused by ultraviolet radiation. Future usage of the device will include studies of time variable emission from solar flares or discrete galactic X-ray sources, and the first major experiment to utilize bent crystal spectrometers will be the Solar Maximum Mission satellite in 1979.

Rapley, C. G.↗
NASA NTRS1976

Stellar crystal X-ray spectroscopy on OSO-8

The large-area graphite crystal X-ray spectrometer on the OSO-8 satellite is described, and its response to stellar line and continuum radiation is discussed. A high resolution X-ray spectrum of Sco X-1 obtained from a preliminary analysis of quick look data shows a strong, smooth continuum with an absence of emission or absorption features over the energy range 2.2 to 8 keV. Upper limits are set on narrow line emission from highly ionized states of S, Ca, and Fe.

Kestenbaum, H. L.↗
DOE OSTI2026

Pressure-Induced Stabilization of Terbium(IV) in CsTb(CrO 4 ) 2 Characterized by X-ray Absorption Spectroscopy

Single crystals of CsTb(CrO 4 ) 2 and CsDy(CrO 4 ) 2 , where the lanthanide metals are in the trivalent state under ambient conditions, have been investigated under high-pressure conditions on the gigapascal scale utilizing a diamond anvil cell. These compounds were characterized by single-crystal X-ray diffraction in addition to high-pressure solid-state UV-vis-NIR spectroscopy, Raman spectroscopy, and Tb L 3 -edge highenergy- resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES). The high-pressure UV-vis-NIR spectra reveal strong broadening of the metal-to-ligand charge transfer band to lower energies, associated with a visible color change from yellow to dark red/black. Clear evidence for the stabilization of Tb 4+ under high pressure is provided by the appearance of a second edge feature characteristic of Tb 4+ , starting at 19.62 GPa in the high-pressure L 3 -edge HERFD-XANES at around 7528 eV. This represents the first example of Tb 4+ being stabilized by high pressure and expands upon the limited chemistry of terbium in the tetravalent state.

Anions↗
DOE OSTI2022

Anti-electrostatic hydrogen-bonded tellurate dimers captured and stabilized by crystallization of a bis-iminoguanidinium salt

Anionic Te 2 O 6 (OH) 4 4– dimers have been captured by crystallization of a hydrated salt of glyoxal-bis-iminoguanidinium (GBIG), and structurally characterized by single-crystal X-ray diffraction and vibrational spectroscopy. The crystal structure reveals anti-electrostatic hydrogen-bonded chains of Te 2 O 6 (OH) 4 4– dimers, consisting of edge-sharing TeO 6 octahedra, stabilized by hydrogen bonding from the GBIG cations and the water molecules included in the crystal. FTIR spectroscopy confirms the presence of TeO 6 octahedra with characteristic Te–O stretching modes at 755 cm -1 and 689 cm -1 , while the observed stretching mode at 3459 cm-1 confirms the presence of axially-bonded hydroxyl groups. Raman spectroscopy and DFT calculations confirm the presence of the Te 2 O 6 (OH) 4 4– dimers in the crystalline phase and of the TeO(OH) 5 – monomers in solution.

36 MATERIALS SCIENCE↗