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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Crystal mechanics-based thermo-elastic constitutive modeling of orthorhombic uranium using generalized spherical harmonics and first-order bounding theories

In earlier works, a mathematical procedure for invertible microstructure-property linkages was developed using computationally efficient spectral methods for polycrystalline cubic and hexagonal metals. This paper formulates such invertible microstructure–property linkages for orthorhombic polycrystalline metals relying on the generalized spherical harmonics (GSH) spectral basis. The procedure is used to compute property closures of orthorhombic polycrystals. The closures represent the complete set of theoretically possible combinations of effective properties for a selected material. The procedure relies on the first-order bounding theories and considers orientation distribution functions (ODFs) as the main microstructural descriptor influencing homogenized properties. Numerous examples of these closures involving second-rank thermal expansion and fourth-rank elastic stiffness tensorial properties over a broad range of temperatures are presented for α-uranium (α-U). In doing so, certain key properties of these closures are exploited to facilitate their computation with drastically reduced computational effort. Along with the recently developed GSH-based interpolation procedure for ODFs from coarsely spaced experimental measurement grids to finely spaced finite element mesh resolution grids presented in Barrett et al., the developed computationally efficient ODF-effective property linkages are used to establish a crystal mechanics-based simulation framework coupled with the finite element method (FEM). The ODF dependent thermal expansion and elastic stiffness tensors are efficiently calculated at every integration point and used by the FEM to predict the overall distortion of a hemispherical part made of α-U during heating. In conclusion, it is shown that the developed framework can be used to simulate microstructurally heterogeneous components under thermo-mechanical loadings in a computationally efficient manner.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Second harmonic generation response of the cubic chalcogenides Ba( 6-x )Sr x [Ag( 4-y )Sn( y/4 )](SnS 4 ) 4

We synthesized the barium/strontium solid solution sequence Ba 6-x Sr x [Ag( 4-y )Sn( y/4 )](SnS 4 ) 4 for nonlinear optical (NLO) applications in the infrared (IR) via a flux synthesis route. All title compounds are isotypic, crystallizing in the cubic space group I$\bar{_4}$ 3d and are composed of a three-dimensional (3D) anionic framework of alternating corner-sharing SnS 4 and AgS 4 tetrahedra charge balanced by Ba and Sr. The shrinkage of Ba/Sr-S bond lengths causes the tetrahedra in the anionic framework to become more distorted, which results in a tunable band gap from 1.58 to 1.38 eV with increasing x values. The performance of the barium limit (x=0) is also superior to that of Sr (x=6), but surprisingly second harmonic generation (SHG) of the solid solution remains strong and is insensitive to the value of x over the range 0-3.8. Results show that the non-type-I phase-matched SHG produced by these cubic chalcogenides display intensities higher than the benchmark AgGaSe 2 from 600 to 1000 nm.

Haynes, Alyssa S.↗
DOE OSTI2021

SHarD: A beam dynamics simulation code for dielectric laser accelerators based on spatial harmonic field expansion

In order to demonstrate acceleration of electrons to relativistic scales by an on chip dielectric laser accelerator (DLA), a ponderomotive focusing scheme capable of capturing and transporting electrons through nanometer-scale apertures over extended interaction lengths has been proposed. Here we present a Matlab-based numerical code (SHarD) utilizing a spatial harmonic expansion of the fields within the dielectric structure to simulate the evolution of the beam phase space distribution in this scheme. The code can be used to optimize key-parameters for the accelerator performance such as the final energy, transverse spot size evolution and total number of electrons accelerated through currently fabricated structures. Eventually, the simulation model will be applied to inform the phase mask profile to be added to a pulse front tilt drive laser pulse using a liquid crystal mask in the experimental setup being assembled at UCLA Pegasus Laboratory.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Beam-energy and collision-system dependence of the linear and mode-coupled flow harmonics from STAR

Recent measurements and hydrodynamic model calculations suggest that the higher-order flow coefficients ν 4 and ν 5 have two contributions: a linear contribution driven by the initial-state eccentricities, εn, and a mode-coupled contribution derived from the lower-order eccentricity coefficients ε 2 and ε 3 . Measurements of these two contributions to ν 4 and ν 5 provide crucial insights to discern initial-state models and to constrain the temperature-dependent specific shear viscosity, η/s, of the plasma produced in heavy-ion collisions. In this work, we have employed the two-subevents cumulant technique to provide the first beam-energy and collision-system dependence of the linear and mode-coupled contributions to the higher-order flow harmonics. Furthermore, our results are shown and discussed for several centrality intervals for U+U collisions at √s NN = 193GeV, Au+Au collisions at √s NN = 200 ,and 54.4GeV and Cu+Au collisions at √s NN = 200GeV. The results are compared with similar studies performed by the ALICE experiment at LHC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems

Recently CMS Collaboration measured mixed-harmonic four-particle azimuthal correlations, known as symmetric cumulants SC(n, m), in pp and p+Pb collisions, and interpreted the non-zero SC(n, m) as evidence for long-range collectivity in these small collision systems. Using the PYTHIA and HIJING models which do not have genuine long-range collectivity, we show that the CMS results, obtained with standard cumulant method, could be dominated by non-flow effects associated with jet and dijets, especially in pp collisions. We show that the non-flow effects are largely suppressed using the recently proposed subevent cumulant methods by requiring azimuthal correlation between two or more pseudorapidity ranges. As a result, we argue that the reanalysis of SC(n, m) using the subevent method in experiments is necessary before they can used to provide further evidences for a long-range multi-particle collectivity and constraints on theoretical models in small collision systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Non-flow effects in three-particle mixed-harmonic azimuthal correlations in small collision systems

The Multi-particle technique has been used to unravel the nature of the long-range collectivity in small collision systems. A large three-particle mixed-harmonic correlation signal was recently observed by the ATLAS Collaboration, but the role of non-flow correlations is not yet studied. We estimate the influence of non-flow correlations to the three-particle correlators in pp and p +Pb collisions using PYTHIA and HIJING models, and compare with the ATLAS results. The large non-flow effects from the jet and dijet production is found to be largely suppressed in p +Pb collisions using the subevent cumulant method by calculating the azimuthal correlation between two or more longitudinal pseudorapidity ranges. Depending on the experimental subevent method, however, the non-flow effects may still be significant in pp collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Transverse-momentum and event-shape dependence of D-meson flow harmonics in Pb–Pb collisions at s NN = 5.02 TeV

The elliptic and triangular flow coefficients v 2 and v 3 of prompt D 0 , D + , and D * + mesons were measured at midrapidity ( | y | < 0.8 ) in Pb–Pb collisions at the centre-of-mass energy per nucleon pair of s NN = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays in the transverse momentum interval 1 < p T < 36 GeV / c in central (0–10%) and semi-central (30–50%) collisions. Compared to pions, protons, and J / ψ mesons, the average D-meson v n harmonics are compatible within uncertainties with a mass hierarchy for p T ≲ 3 GeV / c , and are similar to those of charged pions for higher p T . The coupling of the charm quark to the light quarks in the underlying medium is further investigated with the application of the event-shape engineering (ESE) technique to the D-meson v 2 and p T -differential yields. The D-meson v 2 is correlated with average bulk elliptic flow in both central and semi-central collisions. Within the current precision, the ratios of per-event D-meson yields in the ESE-selected and unbiased samples are found to be compatible with unity. All the measurements are found to be reasonably well described by theoretical calculations including the effects of charm-quark transport and the recombination of charm quarks with light quarks in a hydrodynamically expanding medium.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Beam energy dependence of the linear and mode-coupled flow harmonics in Au+Au collisions

The linear and mode-coupled contributions to higher-order anisotropic flow are presented for Au+Au collisions at √ S NN = 27, 39, 54.4, and 200 GeV and compared to similar measurements for Pb+Pb collisions at the Large Hadron Collider (LHC). The coefficients and the flow harmonics' correlations, which characterize the linear and mode-coupled response to the lower-order anisotropies, indicate a beam energy dependence consistent with an influence from the specific shear viscosity (η/s). In contrast, the dimensionless coefficients, mode-coupled response coefficients, and normalized symmetric cumulants are approximately beam-energy independent, consistent with a significant role from initial-state effects. These measurements could provide unique supplemental constraints to (i) distinguish between different initial-state models and (ii) delineate the temperature (T) and baryon chemical potential (μ B ) dependence of the specific shear viscosity η/s(T, μ B ).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Multiscale assessment of land surface phenology from harmonized Landsat 8 and Sentinel-2, PlanetScope, and PhenoCam imagery

As the spatial and temporal resolution of remotely sensed imagery has improved over the last four decades, algorithms for monitoring and mapping seasonal changes in surface properties have evolved rapidly. Most recently, the availability of daily PlanetScope imagery has created new opportunities for monitoring the land surface phenology (LSP) of terrestrial ecosystems at high spatial resolution. However, the quality and value of LSP information from PlanetScope imagery have not been systematically examined. In this paper, we evaluate the character and quality of LSP information derived from PlanetScope by comparing time series of vegetation indices and LSP metrics from PlanetScope to corresponding time series and LSP metrics derived from Harmonized Landsat 8 and Sentinel-2 (HLS) imagery and PhenoCams at six sites that span a diverse range of land cover types and climate. Results show that vegetation index time series from all three data sources show high temporal correlation, and LSP metrics derived from HLS, PlanetScope, and PhenoCam show high agreement with negligible bias. Semi-variograms for phenometrics estimated from PlanetScope imagery indicate that the majority of spatial variance captured in PlanetScope phenometrics occurs well below the spatial resolution HLS imagery. At the same time, LSP metrics from HLS are most strongly correlated with the 50–75% quantiles of 3 m LSP metrics from PlanetScope. This indicates that HLS captures the average phenology at sub-pixel scale captured in PlanetScope imagery. Here, our results represent the first comprehensive comparison of LSP metrics estimated from PlanetScope and publicly available moderate spatial resolution imagery, and provide insights regarding: (1) the quality and character of LSP metrics derived from HLS and PlanetScope; and (2) the relative merits and trade-offs associated with the use of each data source for LSP studies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Harmonizing solar induced fluorescence across spatial scales, instruments, and extraction methods using proximal and airborne remote sensing: A multi-scale study in a soybean field

Solar-induced chlorophyll fluorescence (SIF) has been widely used to track vegetation photosynthesis at different scales ranging from in-situ measurements to satellite products. Airborne platforms sample SIF data at a spatial scale intermediate between in-situ and satellite, matching that of ground measurement (e.g. flux tower footprints and other field sampling), enabling us to explore causes of SIF variation and validate satellite-based SIF products. However, harmonizing SIF across sensors and platforms (correcting for systematic errors to yield a consistent, comparable SIF product) is challenging because SIF can be retrieved in different absorption windows, with different instruments and methods complicating the comparison between different observational levels (i.e., ground, airborne, satellites) and between sites equipped with different instruments with varying optical properties (spectral resolution and sampling intervals, spatial resolution). Additionally, the spatial and temporal variability of atmospheric properties can influence the retrieval of the weak SIF signal. Because of these complications, direct comparisons of airborne and ground SIF across scales are rarely attempted. Here, in this study, we combined airborne SIF data with simultaneous ‘ground truth’ data collected by stationary and mobile platforms in a soybean field in Nebraska, USA. In this effort, we tested several SIF extraction methods, including Fraunhofer Line Discrimination (FLD), improved Fraunhofer Line Discrimination (iFLD), Spectral Fitting Method (SFM), SpecFit, and a Singular Vector Decomposition (SVD) method. The SpecFit method was sensitive to the 715–740 nm water bands and removing the water bands in the fitting process yielded better agreement between the airborne and ground SIF spectra. Accurate estimation of the ground level downwelling irradiance obtained by ground measurements over a calibration target improved agreement between airborne and ground SIF retrievals at the O 2 A band, and allowed us to derive a SIF dataset with improved agreement across platforms and sampling scales. This experimental approach provided a method for generating comparable SIF signals across instruments, methods and platforms, which is critical to understanding the SIF-GPP relationship at different scales and to cross-validate the diversity of platforms used for satellite products calibration and validation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Interpretation of high-harmonic fast-wave propagation in the scrape-off layer of NSTX-U as a geometrically bounded-waveguide mode

This paper revisits the onset of high-harmonic fast-wave (HHFW) propagation in the scrape-off layer (SOL) plasma of the NSTX/NSTX-U spherical tokamak, motivated by past HHFW heating and current drive experiments and modelling. Previously, the fast-wave propagation in the SOL was correlated with the opening (suppression) of the fast-wave right-hand cutoff layer in front of the antenna. In this work, the SOL propagation is interpreted as a geometric waveguide mode guided by the SOL geometry, whose radial width can be comparable to the wave’s perpendicular wavelength in the HHFW regime. A two-dimensional circular model is first employed using full-wave solvers to characterise the poloidal eigenmode structures and to clarify their relationship to annulus resonance. By progressively adding a tokamak-like magnetic-field configuration, starting from a uniform axial field, the effects of magnetic-field gradients and pitch on the SOL waveguide mode are characterised. The poloidal mode numbers supported by the SOL plasma agree well with analytic estimates, indicating that an anisotropic plasma in a bounded geometry selectively supports and amplifies the resonant poloidal mode number. Additionally, two-dimensional axisymmetric NSTX-U simulations demonstrate that the SOL eigenmode features identified in the circular model persist in the experimentally relevant configurations. A control approach based on lengthening the wave perpendicular wavelength relative to the SOL width, including a higher magnetic (B)-field operation, is discussed. The analysis here shows the key role of a bounded geometry in interpreting HHFW eigenmode coupling and propagation in the NSTX-U SOL plasma.

plasma heating↗
DOE OSTI2017

Second Harmonic Generation Guided Raman Spectroscopy for Sensitive Detection of Polymorph Transitions

Second harmonic generation (SHG) was integrated with Raman spectroscopy for the analysis of pharmaceutical materials. Particulate formulations of clopidogrel bisulfate were prepared in two crystal forms (Form I and Form II). Image analysis approaches enable automated identification of particles by bright field imaging, followed by classification by SHG. Quantitative SHG microscopy enabled discrimination of crystal form on a per particle basis with 99.95% confidence in a total measurement time of ~10 ms per particle. Complementary measurements by Raman and synchrotron XRD are in excellent agreement with the classifications made by SHG, with measurement times of ~1 min and several seconds per particle, respectively. In conclusion, coupling these capabilities with at-line monitoring may enable real-time feedback for reaction monitoring during pharmaceutical production to favor the more bioavailable but metastable Form I with limits of detection in the ppm regime.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

High Speed Intact Protein Characterization Using 4X Frequency Multiplication, Ion Trap Harmonization, and 21 Tesla FTICR-MS

Mass spectrometric characterization of large biomolecules, such as intact proteins, requires the specificity afforded by ultra-high resolution mass measurements performed at both the intact mass and product ion levels. Although the performance of time-of-flight mass analyzers is steadily increasing, the choice of mass analyzer for large biomolecules (e.g. proteins >50 kDa) is generally limited to the Fourier transform family of mass analyzers, such as Orbitrap and ion cyclotron resonance (FTICR-MS) with the latter providing unmatched mass resolving power and measurement accuracy. Yet, protein analyses using FTMS are largely hindered by the low acquisition rates of ultra-high resolution spectra. Frequency multiple detection schemes enable FTICR-MS to overcome this fundamental barrier and achieve resolving powers and acquisition speeds 4X greater than the limits imposed by magnetic field strength. Here we expand upon earlier work on the implementation of this technique for biomolecular characterization. We report the coupling of 21T FTICR-MS, 4X frequency multiplication, ion trapping field harmonization technology, and spectral data processing methods to achieve unprecedented acquisition rates and resolving power in mass spectrometry of large intact proteins. Isotopically resolved spectra of multiply charged ubiquitin ions were acquired using detection periods as short as 12 ms. Large proteins such as apo-transferrin (MW=78 kDa) and monoclonal antibody (MW=150 kDa) were isotopically resolved with detection periods of 384 ms and 768 ms, respectively. These results illustrate the future capability of accurate characterization of large proteins on time-scales compatible with online separations.

Shaw, Jared B.↗
DOE OSTI2016

Phase Transition, Conformational Exchange, and Nonlinear Optical Third Harmonic Generation of A CsP 2 Se 8 ( A = K, Rb, Cs)

The soluble molecular selenophosphate salts ACsP(2)Se(8) (A = K, Rb, Cs) crystallize in the orthorhombic space group Ccce with a = 14.982(3) A, b = 24.579(5) A, and c = 13.065(3) A for the Cs salt and a = 14.782(3) A, b = 23.954(5) A, and c = 13.044(3) A for the K analogue. ACsP2Se8 is composed of the molecular 6-membered ring, [P2Se8](2-), in the twist conformation charge balanced by alkali metals. The band gaps of these compounds are 2.44 +/- 0.2 eV for Cs2P2Se8, 2.41 +/- 0.2 eV for RbCsP2Se8, and 2.36 +/- 0.2 eV for KCsP2Se8. The amorphous versions of these materials can be made by water quenching the melt and have band gaps for all ACsP(2)Se(8) of 2.12 +/- 0.2 eV. Raman spectroscopic studies exhibit active modes of PSe4 and Se Se in the compound. Solution P-31 NMR studies shed light into the interesting conformational fluxionality of the [P2Se8](2-) anion, including a conformation that has not been previously observed. Thermal analysis reveals ACsP(2)Se(8) exhibits a phase transition, which we investigate by in situ synchrotron powder X-ray diffraction. Third harmonic generation (THG) nonlinear optical measurements determined the THG coefficient, chi(3), for amorphous and crystalline Cs2P2Se8 of 1.8 +/- 0.2 X 105 pm(2)/V-2 and 2.4 +/- 0.1 X 105 pm2/V2, respectively.

Haynes, Alyssa S.↗
DOE OSTI2018

Function of Tetrahedral ZnS 3 O Building Blocks in the Formation of SrZn 2 S 2 O: A Phase Matchable Polar Oxysulfide with a Large Second Harmonic Generation Response

Single crystals of a new zinc oxysulfide SrZn 2 S2O were grown in a eutectic KF-KCl flux and the structure was determined by single-crystal X-ray diffraction. SrZn 2 S 2 O crystallizes in the non-centrosymmetric polar space group Pmn2 1 with lattice parameters of a = 3.87440(10) Å, b = 9.9847(3) Å, and c = 6.0916(2) Å. In the crystal structure, close-packed corrugated double layers of ZnS3O tetrahedra, which are derived from the wurtzite structure, are vertically separated by Sr 2+ ions. In addition, the O/S anion ordered arrangement in each close-packed layer yields two distinct orientations of the Zn-centered tetrahedra. The crystals of SrZn 2 S 2 O are colorless and transparent and the oxysulfide has a band gap of 3.86 eV, based on UV-vis-NIR diffuse reflectance measurements. Thermogravimetric measurements showed that SrZn 2 S 2 O is stable up to 650 °C in O 2 gas atmosphere. First-principle calculations indicate that the valence band maximum is mainly composed of O-2p and S-3p states, whereas the conduction band minimum is derived from Zn-4s, Zn-4p, and Sr-4d states. The calculated band dispersion reveals a direct band gap corresponding to a transition between S-3p and Zn-4s energy levels. Second harmonic generation (SHG) measurements determined that SrZn 2 S 2 O is phase matchable with twice the SHG intensity of potassium dihydrogen phosphate (KDP) in contrast to CaZnSO with similar ZnS 3 O building units, which exhibits non-phase matching behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Crystal Growth of Four Oxovanadium(IV) Tartrates Prepared via a Mild Two-Step Hydrothermal Method: Observation of Spin-Dimer Behavior and Second Harmonic Generation

Here, four new oxovanadium(IV) tartrates, namely, A 2 [(VO) 2 (C 4 H 4 O 6 )(C 4 H 2 O 6 )(H 2 O) 2 ]·(H 2 O) 2 , where A = Cs, 1, Rb, 2; K 2 [(VO) 2 (C 4 H 2 O 6 ) 2 (H 2 O) 2 ]·(H 2 O) 2 , 3; and Na 2 [(VO) 2 (C 4 H 4 O 6 )(C 4 H 2 O 6 )(H 2 O) 7 ]·(H 2 O) 2 , 4, were prepared utilizing a two-step, mild hydrothermal route involving l-(+)-tartaric acid as the reducing agent. All four compounds were structurally characterized by single-crystal and powder X-ray diffraction methods and were found to crystallize in the non-centrosymmetric orthorhombic space groups P2 1 2 1 2 1 for 1, 2, and 4 and C222 1 for 3. The temperature dependence of the magnetic susceptibility of these compounds was measured, and 1, 2, and 4 were found to be paramagnetic down to 2 K, while 3 was found to exhibit spin-dimer behavior. Compounds 1, 2, and 3 were found to be second harmonic generation active. Furthermore, all compounds were characterized by IR and UV–vis spectroscopies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Dynamics of Micropollutant Adsorption to Polystyrene Surfaces Probed by Angle-Resolved Second Harmonic Scattering

Angle-resolved second harmonic scattering is used to probe the adsorption dynamics of aqueous cationic and anionic dye molecules onto polystyrene surfaces. The adsorptions of malachite green to negatively charged polystyrene and naphthol yellow S to positively charged polystyrene are both highly favorable, with ΔG Ads values of -10.9 ± 0.2 and -10.27 ± 0.09 kcal/mol, respectively. A competitive displacement methodology was employed to obtain values for the adsorption free energies of various smaller neutral organic molecules, including the important micropollutant ascorbic acid, caffeine, and pentoxifylline. For charged adsorbers, electrostatic interactions appear to significantly contribute to adsorption behavior. However, electrostatic repulsion does not necessarily deter the adsorption of molecules with large uncharged moieties (e.g., surfactants). Lastly, in these cases, the mechanism of adsorption is dominated by van der Waals interactions, with the surface charge playing a relatively minor role.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Imaging Domain Walls in van der Waals Ferroelectrics Using Tip-Enhanced Second Harmonic Generation

van der Waals ferroelectrics have captured significant interest for applications in novel memory and neuromorphic computing devices. Within these materials, interfaces between regions of different ferroelectric polarizations (i.e., domain walls) exhibit distinctive behaviors. Characterization of these behaviors remains a challenge, as domain wall thickness resides at the nanoscale. Using tip-enhanced second harmonic generation (TESHG), we demonstrate nanoscale imaging of domain walls in 2D ferroelectric α-In 2 Se 3 . With a narrow-band near-IR laser, we take advantage of high-wavelength, off-resonant signal enhancement to generate robust and reproducible TESHG. In conclusion, a 16 nm spatial resolution is achieved, and we identify spectral features suggesting that nonlocal effects from domain walls persist nanometers into adjacent domains.

Mantilla, Alexander B. C. [Washington State Univ.,↗