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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Feasibility of hard X-ray imaging using monolithic active pixel sensors (MAPS)

Silicon detectors have been widely used in high energy physics (HEP) experiments. The outstanding properties of silicon detectors include radiation hardness, small material budget, fine spatial resolution, high speed and low cost. In this paper, we report initial results of using a single-bit Monolithic Active Pixel Sensor (MAPS), a leading candidate for the next generation trackers in high luminosity colliders, for hard X-ray imaging. The MAPS responses to X-ray with different energies are obtained and compared with simulation. The observed cluster sizes are larger than that predicted by the Continuous Slowing Down Approximation (CSDA) model, indicating that the charge diffusion process might play an important in the MAPS response to low energy electrons. In conclusion, this work paves the way towards multiple layer ultrafast silicon sensor applications in synchrotrons and XFEL beamlines.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Towards hard x-ray imaging at GHz frame rate

Gigahertz (GHz) imaging using hard x-rays ( Greater-Than-Or-Equivalent-To 10 keV) can be useful to high-temperature plasma experiments, as well as research and applications using coherent photons from synchrotron radiation and x-ray free electron lasers. GHz framing rate can be achieved by using multiple cameras through multiplexing. The advantages and trade-offs of single-photon detection mode, when no more than one x-ray photon is detected per pixel, are given. Two possible paths towards x-ray imaging at GHz frame rates using a single camera are: (a) avalanche photodiode arrays of high-Z materials and (b) microchannel plate photomultipliers in conjunction with materials with large indices of refraction.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Characterizations of MCP performance in the hard x-ray range (6–25 keV)

MCP detector performance at hard x-ray energies from 6 to 25 keV was recently investigated using NSLS beamline X15A at BNL. Measurements were made with an NSTec Gen-II (H-CA-65) framing camera, based on a Photonis MCP with ∼10 μm in diameter pores, ∼12 μm center-center spacing, an L/D ratio of 46, and a bias angle of 8°. The MCP characterizations were focused on (1) energy and angle dependent sensitivity, (2) energy and angle dependent spatial resolution, (3) energy dependent gain performance, and (4) energy dependent dynamic range. These measurement corroborated simulation results using a Monte Carlo model that included hard x-ray interactions and the subsequent electron cascade in the MCP.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se₂ (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO=VBM{sub CIGS} – VBM{sub diamond}=0.3 eV±0.1 eV at the CIGS/Diamond interface and 0.0 eV±0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

The variable hard X-ray emission of NGC 4945 as observed by NuSTAR

We present a broadband (∼0.5-79 keV) spectral and temporal analysis of multiple NuSTAR observations combined with archival Suzaku and Chandra data of NGC 4945, the brightest extragalactic source at 100 keV. We observe hard X-ray (>10 keV) flux and spectral variability, with flux variations of a factor of two on timescales of 20 ks. A variable primary continuum dominates the high-energy spectrum (>10 keV) in all states, while the reflected/scattered flux that dominates at E <10 keV stays approximately constant. From modeling the complex reflection/transmission spectrum, we derive a Compton depth along the line of sight of τ{sub Thomson} ∼ 2.9, and a global covering factor for the circumnuclear gas of ∼0.15. This agrees with the constraints derived from the high-energy variability, which implies that most of the high-energy flux is transmitted rather than Compton-scattered. This demonstrates the effectiveness of spectral analysis at constraining the geometric properties of the circumnuclear gas, and validates similar methods used for analyzing the spectra of other bright, Compton-thick active galactic nuclei (AGNs). The lower limits on the e-folding energy are between 200 and 300 keV, consistent with previous BeppoSAX, Suzaku, and Swift Burst Alert Telescope observations. The accretion rate, estimated from the X-ray luminosity and assuming a bolometric correction typical of type 2 AGN, is in the range ∼0.1-0.3 λ{sub Edd} depending on the flux state. The substantial observed X-ray luminosity variability of NGC 4945 implies that large errors can arise from using single-epoch X-ray data to derive L/L {sub Edd} values for obscured AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film

Hf{sub 1−x−y}Al{sub x}Si{sub y}N (0 ≤ x ≤ 0.14, 0 ≤ y ≤ 0.12) single layer and multilayer films are grown on Si(001) at 250 °C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a single Hf{sub 0.6}Al{sub 0.2}Si{sub 0.2} target in mixed 5%-N{sub 2}/Ar atmospheres at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf{sub 1−x−y}Al{sub x}Si{sub y}N films are controlled by varying the energy E{sub i} of the ions incident at the film growth surface while maintaining the ion-to-metal flux ratio constant at eight. Switching E{sub i} between 10 and 40 eV allows the growth of Hf{sub 0.78}Al{sub 0.10}Si{sub 0.12}N/Hf{sub 0.78}Al{sub 0.14}Si{sub 0.08}N multilayers with similar layer compositions, but in which the Si bonding state changes from predominantly Si–Si/Si–Hf for films grown with E{sub i} = 10 eV, to primarily Si–N with E{sub i} = 40 eV. Multilayer hardness values, which vary inversely with bilayer period Λ, range from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm, while fracture toughness increases directly with Λ. Multilayers with Λ = 10 nm combine relatively high hardness, H ∼ 24 GPa, with good fracture toughness.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Relationship between the Optical Damage Resistance and Radiation Hardness and the Influence of Threshold Effects on the Radiation Hardness of ZnO-Doped LiNbO{sub 3} Crystals

The radiation hardness and optical characteristics of beta-and gamma-irradiated LiNbO{sub 3}〈ZnO〉 crystals have been studied in a wide range of doping levels: ~0.04–5.9 mol % ZnO. The optical absorption (transmission) of the beta-and gamma-irradiated LiNbO{sub 3}〈ZnO〉 crystals has been evaluated as a function of the type and dose of radiation and dopant concentration. The optical damage resistance and radiation hardness of the crystals have been shown to be interrelated and depend on threshold effects in the LiNbO{sub 3}〈ZnO〉 crystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

THE FIRST FOCUSED HARD X-RAY IMAGES OF THE SUN WITH NuSTAR

We present results from the the first campaign of dedicated solar observations undertaken by the Nuclear Spectroscopic Telescope ARray ( NuSTAR ) hard X-ray (HXR) telescope. Designed as an astrophysics mission, NuSTAR nonetheless has the capability of directly imaging the Sun at HXR energies (>3 keV) with an increase in sensitivity of at least two magnitude compared to current non-focusing telescopes. In this paper we describe the scientific areas where NuSTAR will make major improvements on existing solar measurements. We report on the techniques used to observe the Sun with NuSTAR , their limitations and complications, and the procedures developed to optimize solar data quality derived from our experience with the initial solar observations. These first observations are briefly described, including the measurement of the Fe K-shell lines in a decaying X-class flare, HXR emission from high in the solar corona, and full-disk HXR images of the Sun.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The NuSTAR Hard X-Ray Survey of the Norma Arm Region

We present a catalog of hard X-ray sources in a square-degree region surveyed by NuSTAR in the direction of the Norma spiral arm. This survey has a total exposure time of 1.7 Ms, and typical and maximum exposure depths of 50 ks and 1 Ms, respectively. In the area of deepest coverage, sensitivity limits of 5 x 10 -14 and 4 x 10-14 erg s -1 cm -2 in the 3–10 and 10–20 keV bands, respectively, are reached. Twenty-eight sources are firmly detected and ten are detected with low significance; eight of the 38 sources are expected to be active galactic nuclei. The three brightest sources were previously identified as a low-mass X-ray binary, high-mass X-ray binary, and pulsar wind nebula. Based on their X-ray properties and multi-wavelength counterparts, we identify the likely nature of the other sources as two colliding wind binaries, three pulsar wind nebulae, a black hole binary, and a plurality of cataclysmic variables (CVs). The CV candidates in the Norma region have plasma temperatures of ≈10–20 keV, consistent with the Galactic Ridge X-ray emission spectrum but lower than temperatures of CVs near the Galactic Center. This temperature difference may indicate that the Norma region has a lower fraction of intermediate polars relative to other types of CVs compared to the Galactic Center. The NuSTAR logN-logS distribution in the 10–20 keV band is consistent with the distribution measured by Chandra at 2–10 keV if the average source spectrum is assumed to be a thermal model with kT ≈ 15 keV, as observed for the CV candidates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

3FHL: The Third Catalog of Hard Fermi -LAT Sources

We present a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in the first 7 years of data using the Pass 8 event-level analysis. This is the Third Catalog of Hard Fermi -LAT Sources (3FHL), containing 1556 objects characterized in the 10 GeV–2 TeV energy range. The sensitivity and angular resolution are improved by factors of 3 and 2 relative to the previous LAT catalog at the same energies (1FHL). The vast majority of detected sources (79%) are associated with extragalactic counterparts at other wavelengths, including 16 sources located at very high redshift ( z > 2). Of the sources, 8% have Galactic counterparts and 13% are unassociated (or associated with a source of unknown nature). The high-latitude sky and the Galactic plane are observed with a flux sensitivity of 4.4 to 9.5 × 10{sup −11} ph cm{sup −2} s{sup −1}, respectively (this is approximately 0.5% and 1% of the Crab Nebula flux above 10 GeV). The catalog includes 214 new γ -ray sources. The substantial increase in the number of photons (more than 4 times relative to 1FHL and 10 times to 2FHL) also allows us to measure significant spectral curvature for 32 sources and find flux variability for 163 of them. Furthermore, we estimate that for the same flux limit of 10{sup −12} erg cm{sup −2} s{sup −1}, the energy range above 10 GeV has twice as many sources as the range above 50 GeV, highlighting the importance, for future Cherenkov telescopes, of lowering the energy threshold as much as possible.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Hard Carbon as Sodium-Ion Battery Anodes: Progress and Challenges

Hard carbon (HC) is the state-of-the-art anode material for Na-ion batteries due to its excellent overall performance, wide availability and relatively low cost. Recently, tremendous effort has been carried out to elucidate the Na storage mechanism in HC and to explore synthesis approaches that can enhance the performance and lower the cost. However, disputations remain in the fields, particularly on the fundamental questions of ion transfer and storage and the ideal HC structure for high performance. This mini-review aims to give an analysis and summary of the theoretical limitations of HC, discrepancies of the storage mechanism, and methods to improve the performance. In the end, future research on developing ideal structured HC, advanced electrolyte and optimized electrolyte-electrode interphase are proposed on the basis of recent progress.

Xiao, Biwei↗
DOE OSTI2018

Spectroelectrochemical Sensor for Spectroscopically Hard-to-detect Metals by in situ Formation of a Luminescent Complex Using Ru(II) as a Model Compound

Fast, robust, and cost-effective means of detecting spectroscopically inactive metal species are necessary for field detection and applications within a variety of areas including industry and the nuclear safeguards fields. A sensor based on spectroelectrochemistry is an excellent candidate to meet these needs as it provides improved selectivity for specifically quantifying metal ions by simultaneously monitoring at least two physio-chemical properties. Ruthenium was chosen as a model system for this study due to its spectroscopic and electrochemical characteristics as well as its relevance within the fuel cycle and industrial fields. Aqueous Ru displays multiple redox couples in which all available oxidation states have poor sensitivity for detection by visible absorption spectroscopy because of the low molar absorptivities. Ru can, however, form complexes with sensitizing ligands such as 2,2'-bipyridine, where the resulting [Ru(ligand)3]2+ complex displays a red luminescence with a high quantum yield of emission. This significantly improves detection limits for Ru and allows for the spectroelectrochemical detection of the otherwise hard-to-detect metal ion. This work explores the in-situ generation of Ru(bpy)3 complexes in simulated field samples and their subsequent spectroelectrochemical sensing using our sensor methodology.

Lines, Amanda M.↗
DOE OSTI2020

Microstructure, hardness and cavitation erosion resistance of different cold spray coatings on stainless steel 316 for hydropower applications

There is an urgent need for repair of hydropower components that have undergone damage due to cavitation. Conventional repair methods involve melting of materials and can deteriorate material properties and cause distortion. This study investigated the relevant properties of different materials using solid phase processing—cold spray technology. Stainless steel (SS) 316, Inconel 625 and CrC-NiCr materials were cold spray deposited onto base metal SS 316, respectively. Cold spray achieved dense uniform deposits with low level porosity, and intimate contact between the deposit and the base metal was observed. Severe plastic deformation imparted during the cold spray process resulted in significant grain size refinement, nanostructured regions were observed in the deposits across the interfacial area. Cold sprayed deposits exhibited elevated hardness in contrast to that of the base metal SS 316. The cavitation erosion resistance of the deposits was evaluated with a cavitation erosion jet adhering to ASTM G134. Both SS 316 and Inconel 625 achieved better cavitation erosion resistance when compared to that of the SS 316 base metal, with the former exhibiting close to a 4 times improvement.

Jiang, Xiujuan↗
DOE OSTI2012

VERITAS OBSERVATIONS OF SIX BRIGHT, HARD-SPECTRUM FERMI-LAT BLAZARS

We report on VERITAS very high energy (VHE; E {>=} 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and X-Ray Telescope data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars shows a synchrotron peak bordering between the intermediate- and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Enabling liquid solvent structure analysis using hard x-ray absorption spectroscopy with a transferrable microfluidic reactor

In this study, a vacuum compatible microfluidic device, system for analysis at the liquid vacuum interface, is integrated to hard x-ray absorption spectroscopy to obtain the local structure of K 3 [Fe(CN) 6 ] in aqueous solutions with three concentrations of 0.5 M, 0.05 M, and 0.005 M. The solutions were sealed in a microchannel 500 µm wide and 300 µm deep in a portable microfluidic device. The Fe K-edge x-ray absorption spectra indicate a presence of Fe(III) in the complex in water, with an octahedral geometry coordinated with 6 C atoms in the first shell with a distance of ~1.92 Å and 6 N atoms in the second shell with a distance of ~3.10 Å. Varying the concentration has no observable influence on the structure of K 3 [Fe(CN) 6 ]. Our results demonstrate the feasibility of using microfluidic based liquid cells in large synchrotron facilities. Using portable microfludic reactors provides a viable approach to enable multifaceted measurements of liquids in the future.

25 ENERGY STORAGE↗