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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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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Development of Compton X-ray spectrometer for high energy resolution single-shot high-flux hard X-ray spectroscopy

Hard X-ray spectroscopy is an essential diagnostics used to understand physical processes that take place in high energy density plasmas produced by intense laser-plasma interactions. A bundle of hard X-ray detectors, of which the responses have different energy thresholds, is used as a conventional single-shot spectrometer for high-flux (>10{sup 13} photons/shot) hard X-rays. However, high energy resolution (Δhv/hv < 0.1) is not achievable with a differential energy threshold (DET) X-ray spectrometer because its energy resolution is limited by energy differences between the response thresholds. Experimental demonstration of a Compton X-ray spectrometer has already been performed for obtaining higher energy resolution than that of DET spectrometers. In this paper, we describe design details of the Compton X-ray spectrometer, especially dependence of energy resolution and absolute response on photon-electron converter design and its background reduction scheme, and also its application to the laser-plasma interaction experiment. The developed spectrometer was used for spectroscopy of bremsstrahlung X-rays generated by intense laser-plasma interactions using a 200 μm thickness SiO{sub 2} converter. The X-ray spectrum obtained with the Compton X-ray spectrometer is consistent with that obtained with a DET X-ray spectrometer, furthermore higher certainly of a spectral intensity is obtained with the Compton X-ray spectrometer than that with the DET X-ray spectrometer in the photon energy range above 5 MeV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Pilot tone as a key to improving the spatial resolution of eBPMs

At Elettra, the Italian synchrotron light source, an internal project has been started to develop an electron beam position monitor capable of achieving sub-micron resolution with a self-compensation feature. In order to fulfil these requirements, a novel RF front end has been designed. A high isolation coupler combines the input signals with a known pilot tone which is generated by the readout system. This allows the parameters of the four channels to be continuously calibrated, by compensating the different responses of each channel. A similar technique is already known, but for the first time experimental results have shown the improvement in resolution due to this method. The RF chain was coupled with a 4-channel digitizer based on 160 MHz, 16 bits ADCs and an Altera Stratix FPGA. At first, no additional processing was done in the FPGA, collecting only the raw data from the ADCs; the position was calculated through the FFT of each signal. A simulation was also performed to verify the analytic relation between spatial resolution and signal-to-noise ratio; this was very useful to better understand the behaviour of the system with different sources of noise (aperture jitter, thermal noise, etc.). The experimental data were compared with the simulation, showing indeed a perfect agreement with the latter and confirming the capability of the system to reach sub-micrometric accuracy. Therefore, the use of the pilot tone greatly improves the quality of the system, correcting the drifts and increasing the spatial resolution by a factor of 4 in a time window of 24 hours.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

X-ray optical system for imaging laser plumes with a spatial resolution of up to 70 nm

We consider an X-ray optical system which permits obtaining laser plume images at a wavelength of 13.5 nm with a resolution of up to 70 nm. The X-ray optical system comprises an X-ray Schwarzschild objective made up of two aspherical multilayer mirrors, a scintillator (YAG : Ce ceramics), which converts X-rays to the visible radiation, and a visible-optical system, which images the scintillator surface onto a CCD camera. The spatial resolution of the system is limited by the resolution of the optical system (0.7 μm) and the magnification (10{sup ×}) of the X-ray objective and is as high as 70 nm. The effect of Schwarzschild objective mirror shapes on the spatial resolution is analysed. The profile of concave mirror aspherisation is considered, which provides the attainment of the diffraction-limited quality of the objective. Data are given for the quantum efficiency of the system at a wavelength of 13.5 nm. We describe the experimental test bench intended for studying the developed X-ray optical system and outline the first experimental data which illustrate its efficiency. Owing to the natural division into the 'X-ray' and 'visible' parts, the optical system under discussion permits an easy change of the magnification and the field of view without realigning the X-ray optical elements. The wavelength may be varied in a range between 3 and 40 nm by changing the multilayer mirrors. (extreme laser radiation: physics and fundamental applications)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Dynamic super-resolution structured illumination imaging in the living brain

Cells in the brain act as components of extended networks. Therefore, to understand neurobiological processes in a physiological context, it is essential to study them in vivo. Super-resolution microscopy has spatial resolution beyond the diffraction limit, thus promising to provide structural and functional insights that are not accessible with conventional microscopy. However, to apply it to in vivo brain imaging, we must address the challenges of 3D imaging in an optically heterogeneous tissue that is constantly in motion. We optimized image acquisition and reconstruction to combat sample motion and applied adaptive optics to correcting sample-induced optical aberrations in super-resolution structured illumination microscopy (SIM) in vivo. Lastly, we imaged the brains of live zebrafish larvae and mice and observed the dynamics of dendrites and dendritic spines at nanoscale resolution.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

EVOLUTION OF NEAR-SURFACE FLOWS INFERRED FROM HIGH-RESOLUTION RING-DIAGRAM ANALYSIS

Ring-diagram analysis of acoustic waves observed at the photosphere can provide a relatively robust determination of the sub-surface flows at a particular time under a particular region. The depth of penetration of the waves is related to the size of the region, hence the depth extent of the measured flows is inversely proportional to the spatial resolution. Most ring-diagram analysis has focused on regions of extent ∼15° (180 Mm) or more in order to provide reasonable mode sets for inversions. Helioseismic and Magnetic Imager (HMI) data analysis also provides a set of ring fit parameters on a scale three times smaller. These provide flow estimates for the outer 1% (7 Mm) of the Sun only, with very limited depth resolution, but with spatial resolution adequate to map structures potentially associated with the belts and regions of magnetic activity. There are a number of systematic effects affecting the determination of flows from a local helioseismic analysis of regions over different parts of the observable disk, and not all of them are well understood. In this study we characterize those systematic effects with higher spatial resolution so that they may be accounted for more effectively in mapping the temporal and spatial evolution of the flows. Leaving open the question of the mean structure of the global meridional circulation and the differential rotation, we describe the near-surface flow anomalies in time and latitude corresponding to the torsional oscillation pattern in differential rotation and analogous patterns in the meridional cell structure as observed by the Solar Dynamics Observatory/HMI.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

High-resolution imaging of NGC 2346 with GSAOI/GeMS: Disentangling the planetary nebula molecular structure to understand its origin and evolution

We present high spatial resolution (≈60–90 mas) images of the molecular hydrogen emission in the planetary nebula (PN) NGC 2346. The data were acquired during the system verification of the Gemini Multi-conjugate Adaptive Optics System + Gemini South Adaptive Optics Imager. At the distance of NGC 2346, 700 pc, the physical resolution corresponds to ≈56 AU, which is slightly higher than an [N ii] image of NGC 2346 that was obtained with the Hubble Space Telescope/WFPC2. With this unprecedented resolution, for the first time we were able to study the structure of the H{sub 2} gas within the nebula in detail. We found it to be composed of knots and filaments, which at a lower resolution had appeared to be a uniform torus of material. We explain how the formation of the clumps and filaments in this PN are consistent with a mechanism in which a central hot bubble of nebular gas surrounding the central star has been depressurized, and the thermal pressure of the photoionized region drives the fragmentation of the swept-up shell.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

NLTE and LTE Lick indices for red giants from [Fe/H] 0.0 TO −6.0 at SDSS and IDS spectral resolution

We investigate the dependence of the complete system of 22 Lick indices on overall metallicity scaled from solar abundances, [M/H], from the solar value, 0.0, down to the extremely metal-poor (XMP) value of −6.0, for late-type giant stars (MK luminosity class III, logg=2.0) of MK spectral class late-K to late-F (3750<T{sub eff}<6500 K) of the type that are detected as “fossils” of early galaxy formation in the Galactic halo and in extra-galactic structures. Our investigation is based on synthetic index values, I, derived from atmospheric models and synthetic spectra computed with PHOENIX in Local Thermodynamic Equilibrium (LTE) and Non-LTE (NLTE), where the synthetic spectra have been convolved to the spectral resolution, R, of both IDS and SDSS (and LAMOST) spectroscopy. We identify nine indices, that we designate “Lick-XMP,” that remain both detectable and significantly [M/H]-dependent down to [M/H] values of at least ∼−5.0, and down to [M/H] ∼ −6.0 in five cases, while also remaining well-behaved (single-valued as a function of [M/H] and positive in linear units). For these nine indices, we study the dependence of I on NLTE effects, and on spectral resolution. For our LTE I values for spectra of SDSS resolution, we present the fitted polynomial coefficients, C{sub n}, from multi-variate linear regression for I with terms up to third order in the independent variable pairs (T{sub eff}, [M/H] ) and (V−K, [M/H]), and compare them to the fitted C{sub n} values of Worthey et al. at IDS spectral resolution. For this fitted I data-set we present tables of LTE partial derivatives, ((∂I)/(∂T{sub eff}))|{sub [M/H]}, ((∂I)/(∂[M/H]))|{sub T{sub e{sub f{sub f}}}}, ((∂I)/(∂(V−K)))|{sub [M/H]}, and ((∂I)/(∂[M/H]))|{sub (V−K)}, that can be used to infer the relation between a given difference, ΔI, and a difference ΔT{sub eff} or Δ(V−K), or a difference Δ[M/H], while the other parameters are held fixed. For Fe-dominated Lick indices, the effect of NLTE is to generally weaken the value of I at any given T{sub eff} and [M/H] values. As an example of the impact on stellar parameter estimation, for late-type giants of inferred T{sub eff}≳4200 K, an Fe-dominated I value computed in LTE that is too strong might be compensated for by inferring a T{sub eff} value that is too large.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Nanoscale imaging of quantum dot dimers using time-resolved super-resolution microscopy combined with scanning electron microscopy

Abstract Time-resolved super-resolution microscopy was used in conjunction with scanning electron microscopy to image individual colloidal CdSe/CdS semiconductor quantum dots (QD) and QD dimers. The photoluminescence (PL) lifetimes, intensities, and structural parameters were acquired with nanometer scale spatial resolution and sub-nanosecond time resolution. The combination of these two techniques was more powerful than either alone, enabling us to resolve the PL properties of individual QDs within QD dimers as they blinked on and off, measure interparticle distances, and identify QDs that may be participating in energy transfer. The localization precision of our optical imaging technique was ∼3 nm, low enough that the emission from individual QDs within the dimers could be spatially resolved. While the majority of QDs within dimers acted as independent emitters, at least one pair of QDs in our study exhibited lifetime and intensity behaviors consistent with resonance energy transfer from a shorter lifetime and lower intensity donor QD to a longer lifetime and higher intensity acceptor QD. For this case, we demonstrate how the combined super-resolution optical imaging and scanning electron microscopy data can be used to characterize the energy transfer rate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Multimodal hard x-ray imaging with resolution approaching 10 nm for studies in material science

We report multimodal scanning hard x-ray imaging with spatial resolution approaching 10 nm and its application to contemporary studies in the field of material science. The high spatial resolution is achieved by focusing hard x-rays with two crossed multilayer Laue lenses and raster-scanning a sample with respect to the nanofocusing optics. Various techniques are used to characterize and verify the achieved focus size and imaging resolution. Here, the multimodal imaging is realized by utilizing simultaneously absorption-, phase-, and fluorescence-contrast mechanisms. The combination of high spatial resolution and multimodal imaging enables a comprehensive study of a sample on a very fine length scale. In this work, the unique multimodal imaging capability was used to investigate a mixed ionic-electronic conducting ceramic-based membrane material employed in solid oxide fuel cells and membrane separations (compound of Ce 0.8 Gd 0.2 O 2–x and CoFe 2 O 4 ) which revealed the existence of an emergent material phase and quantified the chemical complexity at the nanoscale.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Evaluation of extreme sub-daily precipitation in high-resolution global climate model simulations

We examine the resolution dependence of errors in extreme sub-daily precipitation in available high-resolution climate models. We find that simulated extreme precipitation increases as horizontal resolution increases but that appropriately constructed model skill metrics do not significantly change. We find little evidence that simulated extreme winter or summer storm processes significantly improve with the resolution because the model performance changes identified are consistent with expectations from scale dependence arguments alone. We also discuss the implications of these scale-dependent limitations on the interpretation of simulated extreme precipitation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Nitrogenase MoFe protein from Clostridium pasteurianum at 1.08 Å resolution: comparison with the Azotobacter vinelandii MoFe protein

Determination of the nitrogenase MoFe protein from C. pasteurianum at 1.08 Å resolution and comparison to its distinct ortholog from A. vinelandii at atomic resolution reveals conserved structural arrangements that are significant to the function of nitrogenase. The X-ray crystal structure of the nitrogenase MoFe protein from Clostridium pasteurianum (Cp1) has been determined at 1.08 Å resolution by multiwavelength anomalous diffraction phasing. Cp1 and the ortholog from Azotobacter vinelandii (Av1) represent two distinct families of nitrogenases, differing primarily by a long insertion in the α-subunit and a deletion in the β-subunit of Cp1 relative to Av1. Comparison of these two MoFe protein structures at atomic resolution reveals conserved structural arrangements that are significant to the function of nitrogenase. The FeMo cofactors defining the active sites of the MoFe protein are essentially identical between the two proteins. The surrounding environment is also highly conserved, suggesting that this structural arrangement is crucial for nitrogen reduction. The P clusters are likewise similar, although the surrounding protein and solvent environment is less conserved relative to that of the FeMo cofactor. The P cluster and FeMo cofactor in Av1 and Cp1 are connected through a conserved water tunnel surrounded by similar secondary-structure elements. The long α-subunit insertion loop occludes the presumed Fe protein docking surface on Cp1 with few contacts to the remainder of the protein. This makes it plausible that this loop is repositioned to open up the Fe protein docking surface for complex formation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

High-resolution crystal structures of the solubilized domain of porcine cytochrome b{sub 5}

Crystal structures of the solubilized domain of cytochrome b{sub 5} from porcine liver were determined at sub-angstrom resolution in two crystal forms for both the oxidized and reduced states. The high-resolution structures provided information about the factors that are important for regulating the electronic properties of the haem group of cytochrome b{sub 5}. Mammalian microsomal cytochrome b{sub 5} has multiple electron-transfer partners that function in various electron-transfer reactions. Four crystal structures of the solubilized haem-binding domain of cytochrome b{sub 5} from porcine liver were determined at sub-angstrom resolution (0.76–0.95 Å) in two crystal forms for both the oxidized and reduced states. The high-resolution structures clearly displayed the electron density of H atoms in some amino-acid residues. Unrestrained refinement of bond lengths revealed that the protonation states of the haem propionate group may be involved in regulation of the haem redox properties. The haem Fe coordination geometry did not show significant differences between the oxidized and reduced structures. However, structural differences between the oxidized and reduced states were observed in the hydrogen-bond network around the axial ligand His68. The hydrogen-bond network could be involved in regulating the redox states of the haem group.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Resonant inelastic X-ray scattering spectrometer with 25meV resolution at the Cu K -edge

An unparalleled resolution is reported with an inelastic X-ray scattering instrument at the Cu K -edge. Based on a segmented concave analyzer, featuring single-crystal quartz (SiO 2 ) pixels, the spectrometer delivers a resolution near 25meV (FWHM) at 8981eV. Besides the quartz analyzer, the performance of the spectrometer relies on a four-bounce Si(553) high-resolution monochromator and focusing Kirkpatrick–Baez optics. The measured resolution agrees with the ray-tracing simulation of an ideal spectrometer. The performance of the spectrometer is demonstrated by reproducing the phonon dispersion curve of a beryllium single-crystal.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

High-resolution in-situ characterization of laser powder bed fusion via transmission X-ray microscopy at X-ray free electron lasers

In this work, we describe the instrumentation used to perform the first operando transmission X-ray microscopy (TXM) and simultaneous X-ray diffraction of laser melting simulating laser powder bed fusion on the XCS instrument at the Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL). Our TXM with 40× magnification in the X-ray regime at 11 keV gave spatial resolutions down to 940 nm per line pair, with effective pixel sizes down to 206 nm, image integration times of <100 fs, and frame rates tunable between 2.1 and 119 ns for two probe frames (0.48 GHz to 8.4 MHz). Images were recorded on Zyla and Icarus (UXI) detectors to trade off between spatial resolution and time dynamics. A 1 kW CW IR laser was coupled into the interaction point to conduct pump–probe studies of laser melting and solidification dynamics. Our temporal and spatial resolution with attenuation-based contrast exceeds that currently possible with synchrotron-based high-speed radiography. This system was sensitive to feature velocities of 10–12000 m s −1 but we did not observe any motion in this range in the laser melting of Al6061 alloy. Shockwaves were not observed and hot cracking proceeded at velocities below the detection limits. Pore accumulation was observed between successive shots, indicating that bubble escape mechanisms were not active. With proper experimental design, the spatial resolution, contrast and field of view could be further improved or modified. The increased brightness and narrower bandwidth of the XFEL allowed for this imaging technique and it lays the groundwork for a wide range of operando techniques to study additive manufacturing.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Nonproportionality of Scintillator Detectors. IV. Resolution Contribution from Delta-Rays

This paper is the fourth in a series of articles published on the light yield nonproportionality of scintillators and its impact on the detector's energy resolution. Herein, we focus on modeling the resolution degradation induced by delta-rays. To do this, we begin with Møller's classic equation to describe collisions between incident high-energy electrons and those in the scintillator medium, which lead to the delta-rays. The trajectories of delta-rays having energies above a specified cut-off value are further analyzed to determine the resolution degradation induced by fluctuations in their light yield and ionization density. Our conclusion is that the delta-ray contribution to resolution is typically smaller but comparable to that arising from the primary electron. We have considered the cases for two illustrative scintillators: NaI(Tl) and LSO(Ce)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Improved Localization Precision and Angular Resolution of a Cylindrical, Time-Encoded Imaging System From Adaptive Detector Movements

To the first order, the localization precision and angular resolution of a cylindrical, time-encoded imaging (c-TEI) system is governed by the geometry of the system. Improving either measure requires increasing the mask radius or decreasing the detector diameter, both of which are undesirable. Here, we propose an alternative option of repositioning the detector within the mask to increase the detector-to-mask distance in the direction of a source, thereby improving the localization precision and angular resolution in that direction. Since the detector-to-mask distance only increases for a small portion of the field of view (FOV), we propose implementing adaptive imaging where one leverages data collected during the measurement to optimize the system configuration. This article utilizes both simulations and experiments to set upper bounds on the potential gain from adaptive detector movements for one and two sources in the FOV. When only one source is present, adaptive detector movements can improve the localization precision and angular resolution by 20% for a source at 90 cm and by 32% for a far-field source. When two sources are present, adaptive detector movements can improve localization precision and angular resolution by up to 50% for sources that are ~10° apart (90 cm from the system). We experimentally verify these results through maximum likelihood estimation of the source position(s) and image reconstruction of point sources that are close together. As a demonstration of an adaptive imaging algorithm, we image a complex arrangement of special nuclear material at the Zero Power Physics Reactor facility at Idaho National Laboratory.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
DOE OSTI2025

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

The 2-D position sensitive neutron detectors featuring a significantly improved count rate capacity and a sub-mm spatial resolution are in high demand by neutron scattering facilities, especially the next generation high-flux spallation neutron sources (SNSs). They are anticipated to play a crucial role in fully utilizing the unprecedentedly high neutron brightness offered by these sources. In this work, a high rate and high spatial resolution neutron Anger camera has been successfully developed based on a Ce-doped microcolumnar LiI scintillator film and the PETsys TOFPET2 ASIC readout electronics. The performance evaluation was conducted in a standard laboratory environment as well as the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) with regard to light yield, γ-ray sensitivity, neutron detection efficiency, count rate capability, spatial resolution, and position linearity. The LiI:Ce scintillator was found to have a higher light yield and a lower γ-ray sensitivity than GS20 (i.e., 11729 versus 6000 photons/n and 1.67 × 10 −5 versus on the order of 10 −4 ). The neutron detection efficiency was measured to be 63% at 4.2 Å. This camera demonstrated an exceptional count rate capability, up to at least 481 kHz without rate loss. The spatial resolution was as good as 0.47 mm. Here, the position linearity was also enhanced.

High rate↗
DOE OSTI2016

High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 2, photon noise theory

High-resolution broadband spectroscopy at near-infrared (NIR) wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar, with the TEDI interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec NIR echelle spectrograph. These are the first multidelay EDI demonstrations on starlight. We demonstrated very high (10×) resolution boost and dramatic (20× or more) robustness to point spread function wavelength drifts in the native spectrograph. Data analysis, results, and instrument noise are described in a companion paper (part 1). This part 2 describes theoretical photon limited and readout noise limited behaviors, using simulated spectra and instrument model with noise added at the detector. We show that a single interferometer delay can be used to reduce the high frequency noise at the original resolution (1× boost case), and that except for delays much smaller than the native response peak half width, the fringing and nonfringing noises act uncorrelated and add in quadrature. This is due to the frequency shifting of the noise due to the heterodyning effect. We find a sum rule for the noise variance for multiple delays. The multiple delay EDI using a Gaussian distribution of exposure times has noise-to-signal ratio for photon-limited noise similar to a classical spectrograph with reduced slitwidth and reduced flux, proportional to the square root of resolution boost achieved, but without the focal spot limitation and pixel spacing Nyquist limitations. At low boost (~1×) EDI has ~1.4× smaller noise than conventional, and at >10× boost, EDI has ~1.4× larger noise than conventional. Readout noise is minimized by the use of three or four steps instead of 10 of TEDI. Net noise grows as step phases change from symmetrical arrangement with wavenumber across the band. As a result, for three (or four) steps, we calculate a multiplicative bandwidth of 1.8:1 (2.3:1), sufficient to handle the visible band (400 to 700 nm, 1.8:1) and most of TripleSpec (2.6:1).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗