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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

We applied small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques in order to study the microstructure of several New Albany shales of different maturity. It has been established that the total porosity decreases with maturity and increases somewhat for post-mature samples. One new method of SANS data analysis was developed, which allows the extraction of information about the size range and number density of micropores from the relatively flat scattering intensity observed in the limit of the large scattering vector Q. Macropores and significant number of mesopores are surface fractals, and their structure can be described in terms of the polydisperse spheres (PDSP) model. The model-independent Porod invariant method was employed to estimate total porosity, and the results were compared with the PDSP model results. It has been demonstrated that independent evaluation of incoherent background is crucial for accurate interpretation of the scattering data in the limit of large Q-values. Moreover, pore volumes estimated by the N-2 and CO 2 adsorption, as well as via the mercury intrusion technique, have been compared with those measured by SANS/USANS, and possible reasons for the observed discrepancies are discussed.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2016

The life science x-ray scattering beamline at NSLS-II

We report the current development status of the High Brightness X-ray Scattering for Life Sciences (or Life Science X-ray Scattering, LiX) beamline at the NSLS-II facility of Brookhaven National Laboratory. This instrument will operate in the x-ray energy range of 2.1-18 keV, provide variable beam sizes from 1 micron to ∼0.5 mm, and support user experiments in three scientific areas: (1) high-throughput solution scattering, in-line size exclusion chromatography and flow mixers-based time-resolved solution scattering of biological macro-molecules, (2) diffraction from single- and multi-layered lipid membranes, and (3) scattering-based scanning probe imaging of biological tissues. In order to satisfy the beam stability required for these experiments and to switch rapidly between different types of experiments, we have adopted a secondary source with refractive lenses for secondary focusing, a detector system consisting of three Pilatus detectors, and specialized experimental modules that can be quickly exchanged and each dedicated to a defined set of experiments. The construction of this beamline is on schedule for completion in September 2015. User experiments are expected to start in Spring 2016.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Robust Optical Richness Estimation with Reduced Scatter

Reducing the scatter between cluster mass and optical richness is a key goal for cluster cosmology from photometric catalogs. We consider various modifications to the red-sequence matched filter richness estimator of Rozo et al. (2009b), and evaluate their impact on the scatter in X-ray luminosity at fixed richness. Most significantly, we find that deeper luminosity cuts can reduce the recovered scatter, finding that {sigma}{sub ln L{sub X}|{lambda}} = 0.63 {+-} 0.02 for clusters with M{sub 500c} {approx}> 1.6 x 10{sup 14} h{sub 70}{sup -1} M{sub {circle_dot}}. The corresponding scatter in mass at fixed richness is {sigma}{sub ln M|{lambda}} {approx} 0.2-0.3 depending on the richness, comparable to that for total X-ray luminosity. We find that including blue galaxies in the richness estimate increases the scatter, as does weighting galaxies by their optical luminosity. We further demonstrate that our richness estimator is very robust. Specifically, the filter employed when estimating richness can be calibrated directly from the data, without requiring a-priori calibrations of the red-sequence. We also demonstrate that the recovered richness is robust to up to 50% uncertainties in the galaxy background, as well as to the choice of photometric filter employed, so long as the filters span the 4000 {angstrom} break of red-sequence galaxies. Consequently, our richness estimator can be used to compare richness estimates of different clusters, even if they do not share the same photometric data. Appendix A includes 'easy-bake' instructions for implementing our optimal richness estimator, and we are releasing an implementation of the code that works with SDSS data, as well as an augmented maxBCG catalog with the {lambda} richness measured for each cluster.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

The CU 2-D-MAX-DOAS instrument – Part 2: Raman scattering probability measurements and retrieval of aerosol optical properties

Abstract. The multiannual global mean of aerosol optical depth at 550 nm (AOD550) over land is ∼ 0.19, and that over oceans is ∼ 0.13. About 45 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions. We present an inherently calibrated retrieval (i.e., no need for radiance calibration) to simultaneously measure AOD and the aerosol phase function parameter, g, based on measurements of azimuth distributions of the Raman scattering probability (RSP), the near-absolute rotational Raman scattering (RRS) intensity. We employ radiative transfer model simulations to show that for solar azimuth RSP measurements at solar elevation and solar zenith angle (SZA) smaller than 80°, RSP is insensitive to the vertical distribution of aerosols and maximally sensitive to changes in AOD and g under near-molecular scattering conditions. The University of Colorado two-dimensional Multi-AXis Differential Optical Absorption Spectroscopy (CU 2-D-MAX-DOAS) instrument was deployed as part of the Two Column Aerosol Project (TCAP) at Cape Cod, MA, during the summer of 2012 to measure direct sun spectra and RSP from scattered light spectra at solar relative azimuth angles (SRAAs) between 5 and 170°. During two case study days with (1) high aerosol load (17 July, 0.3 < AOD430 < 0.6) and (2) near-molecular scattering conditions (22 July, AOD430 < 0.13) we compare RSP-based retrievals of AOD430 and g with data from a co-located CIMEL sun photometer, Multi-Filter Rotating Shadowband Radiometer (MFRSR), and an airborne High Spectral Resolution Lidar (HSRL-2). The average difference (relative to DOAS) for AOD430 is +0.012 ± 0.023 (CIMEL), −0.012 ± 0.024 (MFRSR), −0.011 ± 0.014 (HSRL-2), and +0.023 ± 0.013 (CIMELAOD − MFRSRAOD) and yields the following expressions for correlations between different instruments: DOASAOD = −(0.019 ± 0.006) + (1.03 ± 0.02) × CIMELAOD (R2 = 0.98), DOASAOD = −(0.006 ± 0.005) + (1.08 ± 0.02) × MFRSRAOD (R2 = 0.98), and CIMELAOD = (0.013 ± 0.004) + (1.05 ± 0.01) × MFRSRAOD (R2 = 0.99). The average g measured by DOAS on both days was 0.66 ± 0.03, with a difference of 0.014 ± 0.05 compared to CIMEL. Active steps to minimize the error in the RSP help to reduce the uncertainty in retrievals of AOD and g. As AOD decreases and SZA increases, the RSP signal-to-noise ratio increases. At AOD430 ∼ 0.4 and 0.10 the absolute AOD errors are ∼ 0.014 and 0.003 at 70° SZA and 0.02 and 0.004 at 35° SZA. Inherently calibrated, precise AOD and g measurements are useful to better characterize the aerosol direct effect in urban polluted and remote pristine environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Neutron scattering measurement of water content and chemical composition of alkali-glass powder reacted gel

Highlights: • Water absorption ability of alkali-glass powder reacted gel was largely reduced comparing other reported alkali-silica gels. • Both SAXS and SANS results showed similar internal structures of samples prepared with different H2O:D2O mixing ratios. • Neutron scattering method was developed to non-destructively determine gel water content and mass density of reacted gels. • Neutron scattering methods (based on scattering length density) on gel water content was validated with TGA measurement. - Abstract: Recent studies demonstrated that the added glass powder with high-alumina content could significantly reduce Alkali-Silica Reaction (ASR) damage in cement concrete. This paper aims to investigate the gel water content, chemical composition and expansion behavior of the alkali-glass powder reacted gel by using neutron scattering and other characterization techniques. Three types of samples were prepared with glass powder, sodium oxide and deuteroxide/hydrogen water with different molar ratios. The swelling potential of this alkali-glass powder reacted gel was much lower than that of the reported alkali-silica reacted gel. The gel water content and chemical compositions were characterized with small-angle neutron scattering (SANS) technique, supported by small-angle X-ray scattering (SAXS), prompt-gamma ray neutron activation analysis (PGAA) measurement. The SAXS test results showed the close scattering intensities, and thus similar internal microstructures among these samples. The elemental molar ratios of gels were obtained from the PGAA test results. Then the gel water molar ratio and mass density were determined by neutron scattering contrast calculation. The determined gel water content from neutron scattering analysis was validated with zero contrast analysis and TGA experimental measurement. Overall, this paper demonstrated the feasibility of using SANS technique to determine the water content of alkali-glass powder reacted gel.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

Lavelle, Christopher M↗
DOE OSTI2016

An X-ray and Neutron Scattering Study of the Formation of Core-Shell Type Polyoxometalates

A typical type of core-shell polyoxometalates can be obtained through the Keggin-type polyoxometalatetemplated growth of a layer of spherical shell structure of {Mo72Fe30}. Small angle X-ray scattering is used to study the structural features and stability of the core-shell structures in aqueous solutions. Timeresolved small angle X-ray scattering is applied to monitor the synthetic reactions and a three-stage formation mechanism is proposed to describe the synthesis of the core-shell polyoxometalates based on the monitoring results. New protocols have been developed by fitting the X-ray data with customed physical models, which provide more convincing, objective, and completed data interpretation. Quasielastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core-shell structures and two different types of water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures.

Yin, Panchao↗
DOE OSTI2014

Poster — Thur Eve — 07: Simultaneous reconstruction of both true and scattered coincidences using a Generalized Scatter reconstruction algorithm in PET

Introduction: Scattered coincidences in PET are generally taken as noise, which reduces image contrast and compromises quantification. We have developed a method, with promising results, to reconstruct activity distribution from scattered PET events instead of simply correcting for them. The implementation of this method on clinical PET scanners is however limited by the currently available detector energy resolution. With low energy resolution we lose the ability to distinguish scattered coincidences from true events based on the measured photon energy. In addition the two circular arcs used to confine the source position for a scattered event cannot be accurately defined. Method: This paper presents a modification to this approach which accounts for limited energy resolution. A measured event is split into a true and a scattered component each with different probabilities based on the position of the pair of photon energies in the energy spectrum. For the scattered component, we model the photon energy with a Gaussian distribution and the upper and lower energy limits can be estimated and used to define inner and outer circular arcs to confine the source position. The true and scattered components for each measured event were reconstructed using our Generalized Scatter reconstruction algorithm. Results and Conclusion: The results show that the contrast and noise properties were improved by 6–9% and 2–4% respectively. This demonstrates that the performance of the algorithm is less sensitive to the energy resolution and that incorporating scattered photons into reconstruction brings more benefits than simply rejecting them.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Simultaneous measurements of forward Thomson scattering and rotational Raman scattering in a weakly ionized plasma

This paper demonstrates a simultaneous Thomson scattering and rotational Raman scattering spectroscopy in a weakly ionized plasma in air. Thomson scattering was collected in the forward scattering direction, in order to compress the relative spectra width of Thomson scattering from the plasma. Simultaneous measurements of rotational Raman scattering were obtained in the same direction, which was not affected by the collection angles. The measurements thus yielded electron temperature (T e ) and electron number density (n e ) as well as gas temperature in a weakly ionized atmospheric pressure plasma. The separation of rotational Raman scattering and Thomson scattering occurred when the scattering angle decreased to 20 degrees in the plasma, where the air temperature was found to be 150 ± 25 °C, and electron temperature of the plasma was 0.587 ± 0.087 eV, and electron number density was (1.608 ± 0.416) × 1021 m-3. The technique could be used for various plasma and combustion diagnostics in realistic engineering environments.

He, Zichen (ORCID:0000000183159882)↗
NASA NTRS1992

Lidar measurements of cloud extinction coefficient distribution and its forward scattering phase function according to multiply scattered lidar returns

The study of the inversion algorithm for the single scatter lidar equation, for quantitative determination of cloud (or aerosol) optical properties, has received much attention over the last thirty years. Some of the difficulties associated with the solution of this equation are not yet solved. One problem is that a single scatter lidar equation has two unknowns. Because of this, the determination of the far-end boundary value, in the case of Klett's algorithm, is a problem if the atmosphere is optically inhomogeneous. Another difficulty concerns multiple scattering. There is a large error in the extinction distribution solution, in many cases, if only the single scattering component is considered, while neglecting the multiple scattering component. However, the use of multiple scattering in the remote sensing of aerosol or cloud optical properties is promising. In our early study, an inversion method for simultaneous determination of the cloud (or aerosol) Extinction Coefficient Distribution (ECD) and its Forward Scattering Phase Function (FSPF) was proposed according to multiply scattered lidar returns with two fields of view for the receiver. The method is based on a parameterized multiple scatter lidar equation. This paper is devoted to further numerical tests and an experimental study of lidar measurements of cloud ECD and FSPF using this method.

Qiu, Jinhuan↗
DOE OSTI2012

Contrast-Matched Small-Angle X-ray Scattering from a Heavy-Atom-Labeled Protein in Structure Determination: Application to a Lead-Substituted Calmodulin-Peptide Complex

The information content in 1-D solution X-ray scattering profiles is generally restricted to low-resolution shape and size information that, on its own, cannot lead to unique 3-D structures of biological macromolecules comparable to all-atom models derived from X-ray crystallography or NMR spectroscopy. Here we show that contrast-matched X-ray scattering data collected on a protein incorporating specific heavy-atom labels in 65% aqueous sucrose buffer can dramatically enhance the power of conventional small- and wide-angle X-ray scattering (SAXS/WAXS) measurements. Under contrast-matching conditions the protein is effectively invisible and the main contribution to the X-ray scattering intensity arises from the heavy atoms, allowing direct extraction of pairwise distances between them. In combination with conventional aqueous SAXS/WAXS data, supplemented by NMR-derived residual dipolar couplings (RDCs) measured in a weakly aligning medium, we show that it is possible to position protein domains relative to one another within a precision of 1 Å. We demonstrate this approach with respect to the determination of domain positions in a complex between calmodulin, in which the four Ca 2+ ions have been substituted by Pb 2+ , and a target peptide. The uniqueness of the resulting solution is established by an exhaustive search over all models compatible with the experimental data, and could not have been achieved using aqueous SAXS and RDC data alone. Moreover, we show that the correct structural solution can be recovered using only contrast-matched SAXS and aqueous SAXS/WAXS data.

Grishaev, Alexander↗
DOE OSTI2013

Resonant electromagnetic scattering in anisotropic layered media

The resonant excitation of an electromagnetic guided mode of a slab structure by exterior radiation results in anomalous scattering behavior, including sharp energy-transmission anomalies and field amplification around the frequency of the slab mode. In the case of a periodically layered ambient medium, anisotropy serves to couple the slab mode to radiation. Exact expressions for scattering phenomena are proved by analyzing a pole of the full scattering matrix as it moves off the real frequency axis into the lower half complex plane under a detuning of the wavevector parallel to the slab. The real pole is the frequency of a perfect (infinite Q) guided mode, which becomes lossy as the frequency gains an imaginary part. This work extends results of Shipman and Venakides to evanescent source fields and two-dimensional parallel wavevector and demonstrates by example how the latter allows one to control independently the width and central frequency of a resonance by varying the angle of incidence of the source field. The analysis relies on two nondegeneracy conditions of the complex dispersion relation for slab modes (relating poles of the scattering matrix to wavevector), which were assumed in previous works and are proved in this work for layered media. One of them asserts that the dispersion relation near the wavevector κ and frequency ω of a perfect guided mode is the zero set of a simple eigenvalue ℓ(κ, ω), and the other relates ∂ℓ/∂ω to the total energy of the mode, thereby implying that this derivative is nonzero.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Portable diagnostic package for Thomson scattering and optical emission spectroscopy on Princeton field-reversed configuration 2 (PFRC 2)

An Advanced Research Projects Agency-Energy funded diagnostic system has been deployed to the Princeton field-reversed configuration 2 (PFRC-2) device, located at Princeton Plasma Physics Laboratory. The Portable Diagnostic Package (PDP), designed at Oak Ridge National Laboratory, allows for the measurement of Thomson Scattering (TS) for electron density and temperature and Optical Emission Spectroscopy (OES) for ion temperature, impurity density, and ion velocity. A tunable spectrometer on the PDP with three gratings provides the flexibility to measure low (1 eV) and high (1000 eV) electron temperature ranges from TS. Additionally, using a second spectrometer, the OES diagnostic can survey light emission from various ion excitation levels for wide wavelength ranges. The electron density (<2 × 10 19 m –3 ) of plasmas generated in PFRC-2 has been below the PDP TS discrimination threshold, which has made TS signal detection challenging against a high-background of laser stray light. The laser stray light was iteratively reduced by making modifications to the entrance and exit geometry on PFRC-2. Rayleigh scattering experiments on PFRC have yielded the TS discrimination sensitivity to be >1 × 10 20 m –3 for the PDP. A recently implemented narrow-band notch spectral filter that masks the second harmonic 532 nm Nd:YAG laser wavelength has increased the system’s TS light discrimination sensitivity 65 times compared to the instance when the notch filter was not implemented. The hardware implementation including design changes to the flight tubes and Brewster windows will be discussed, along with results from Rayleigh and rotational Raman scattering sensitivity analyses, which were used to establish a quantitative figure of merit on the system performance. Further, the Raman scattering calibration with the notch filter has improved the PDP electron density threshold to 1 ± 0.5 × 10 18 m –3 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Interference in electron–molecule elastic scattering

General formulas describing the multiple scattering of electron by polyatomic molecules have been derived within the framework of the model of non-overlapping atomic potentials. These formulas are applied to different carbon molecules, both for fixed-in-space and randomly oriented molecules. Here, the molecular continuum wave function is represented as a plane wave plus a linear combination of the Green’s functions for free motion and the derivatives of these functions. Far from the target the electron spherical waves interfere as in the case of the Young’s double slits experiment. This interference manifests itself as diffraction oscillations in the differential and total cross sections for elastic electron scattering. The amplitude of electron scattering by a molecule is defined by the phase shifts for each of the atoms forming the target and its geometry. The numerical calculation of the scattering amplitude in closed form (rather than in the form of S-matrix expansion) is reduced to solving a system of algebraic equations. The number of atoms in a molecule and the atomic phase shifts for the orbital angular momenta included in the calculation define the number of equations.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

An algebraic convolution formulation for multiple-scattering correction in small-angle neutron scattering

Multiple scattering in small-angle neutron scattering (SANS) redistributes spectral weight and distorts structural interpretation, particularly for thick or strongly scattering samples. We develop a finite-dimensional spectral desmearing framework that corrects multiple scattering without resorting to integral transforms or model-dependent extrapolation. The primary intensity is expanded in an orthonormal basis adapted to the isotropic transverse-momentum measure, under which convolution reduces to a recursive tensor contraction, allowing the Poisson-weighted multiple-scattering series to be evaluated directly in a finite-dimensional basis representation. This formulation yields a stable forward–inverse mapping between apparent and primary spectra. Numerical tests demonstrate convergence under repeated convolution and accurate recovery of the single-scattering intensity. Application to SANS measurements collected at multiple neutron facilities, including the Spallation Neutron Source, the High Flux Isotope Reactor, and the Institut Laue-Langevin, shows the quantitative reconstruction of the underlying primary spectrum across a wide range of transmission conditions, including strongly attenuating samples. Here, the method provides a stable, model-agnostic framework for multiple-scattering correction in SANS and enables consistent structural interpretation across instruments and scattering regimes.

Tung, Chi-Huan [Oak Ridge National Laboratory (ORN↗