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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Radiation hardness assessment of the charge-integrating hybrid pixel detector JUNGFRAU 1.0 for photon science

JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications in free electron lasers, particularly SwissFEL, and synchrotron light sources. JUNGFRAU is an automatic gain switching, charge-integrating detector which covers a dynamic range of more than 10{sup 4} photons of an energy of 12 keV with a good linearity, uniformity of response, and spatial resolving power. The JUNGFRAU 1.0 application-specific integrated circuit (ASIC) features a 256 × 256 pixel matrix of 75 × 75 μm{sup 2} pixels and is bump-bonded to a 320 μm thick Si sensor. Modules of 2 × 4 chips cover an area of about 4 × 8 cm{sup 2}. Readout rates in excess of 2 kHz enable linear count rate capabilities of 20 MHz (at 12 keV) and 50 MHz (at 5 keV). The tolerance of JUNGFRAU to radiation is a key issue to guarantee several years of operation at free electron lasers and synchrotrons. The radiation hardness of JUNGFRAU 1.0 is tested with synchrotron radiation up to 10 MGy of delivered dose. The effect of radiation-induced changes on the noise, baseline, gain, and gain switching is evaluated post-irradiation for both the ASIC and the hybridized assembly. The bare JUNGFRAU 1.0 chip can withstand doses as high as 10 MGy with minor changes to its noise and a reduction in the preamplifier gain. The hybridized assembly, in particular the sensor, is affected by the photon irradiation which mainly shows as an increase in the leakage current. Self-healing of the system is investigated during a period of 11 weeks after the delivery of the radiation dose. Annealing radiation-induced changes by bake-out at 100 °C is investigated. It is concluded that the JUNGFRAU 1.0 pixel is sufficiently radiation-hard for its envisioned applications at SwissFEL and synchrotron beam lines.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Hard x-ray nanoprobe of beamline P06 at PETRA III

The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large user community, from physics, chemistry, and nanotechnology to the bio-medical, materials, environmental, and geosciences. It has been in user operation since 2012, and is mainly based on nanofocusing refractive x-ray lenses. Using refractive optics, nearly gaussian-limited nanobeams in the range from 50 to 100 nm can be generated in the hard x-ray energy range from 8 to 30 keV. The degree of coherence can be traded off against the flux in the nanobeam by a two-stage focusing scheme. We give a brief overview on published results from this instrument and describe its most important components and parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Improvement of density resolution in short-pulse hard x-ray radiographic imaging using detector stacks

We demonstrate that stacking several imaging plates (IPs) constitutes an easy method to increase hard x-ray detection efficiency. Used to record x-ray radiographic images produced by an intense-laser driven hard x-ray backlighter source, the IP stacks resulted in a significant improvement of the radiograph density resolution. We attribute this to the higher quantum efficiency of the combined detectors, leading to a reduced photon noise. Electron-photon transport simulations of the interaction processes in the detector reproduce the observed contrast improvement. Increasing the detection efficiency to enhance radiographic imaging capabilities is equally effective as increasing the x-ray source yield, e.g., by a larger drive laser energy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Hardness and microstructural inhomogeneity at the epitaxial interface of laser 3D-printed Ni-based superalloy

Here in this letter, microstructural and mechanical inhomogeneities, a great concern for single crystal Ni-based superalloys repaired by laser assisted 3D printing, have been probed near the epitaxial interface. Nanoindentation tests show the hardness to be uniformly lower in the bulk of the substrate and constantly higher in the epitaxial cladding layer. A gradient of hardness through the heat affected zone is also observed, resulting from an increase in dislocation density, as indicated by the broadening of the synchrotron X-ray Laue microdiffraction reflections. Lastly, the hardening mechanism of the claddin g region, on the other hand, is shown to originate not only from high dislocation density but also and more importantly from the fine γ/γ' microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Discovering exceptionally hard and wear-resistant metallic glasses by combining machine-learning with high throughput experimentation

Lack of crystalline order in amorphous alloys, commonly called metallic glasses (MGs), tends to make them harder and more wear-resistant than their crystalline counterparts. However, finding inexpensive MGs is daunting; finding one with enhanced wear resistance is a further challenge. Relying on machine learning (ML) predictions of MGs alone requires a highly precise model; however, incorporating high-throughput (HiTp) experiments into the search rapidly leads to higher performing materials even from moderately accurate models. Here, we exploit this synergy between ML predictions and HiTp experimentation to discover new hard and wear-resistant MGs in the Fe–Nb–B ternary material system. Several of the new alloys exhibit hardness greater than 25 GPa, which is over three times harder than hardened stainless steel and only surpassed by diamond and diamond-like carbon. This ability to use less than perfect ML predictions to successfully guide HiTp experiments, demonstrated here, is especially important for searching the vast Multi-Principal-Element-Alloy combinatorial space, which is still poorly understood theoretically and sparsely explored experimentally.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Versatile multi-energy hard x-ray camera to study confined and unconfined fast electron dynamics and anisotropies (Invited)

A powerful and flexible hard x-ray (HXR) camera has been recently installed and tested on the WEST tokamak (CEA, France) in collaboration with the Princeton Plasma Physics Laboratory. The diagnostic is a pinhole camera fielded with a 2D pixel detector equipped with a 1 mm thick CdTe sensor. The novelty of this diagnostic technique is the detector’s capability of adjusting the threshold energy at the pixel level. This innovation provides great flexibility in the energy configuration, allowing simultaneous space, energy, and time resolved x-ray measurements. The novel camera has been used to measure the core radiation from non-Maxwellian (fast) electrons accelerated by Lower Hybrid (LH) waves and also the beam–target emission of tungsten in the divertor region produced by fast electron losses interacting with the target. In addition, anisotropic hard x-ray emission has been detected for the first time at the WEST core and edge plasma, with opposite toroidal intensity trends. Finally, experimental vertical and toroidal HXR profiles have been successfully reproduced with the LH code LUKE.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Advanced monolithic 2D multilayer Laue lens (MLL) optics for hard x-ray nanofocusing and nanotomography

We report on the development of a new generation of monolithic two-dimensional (2D) multilayer Laue lens (MLL) optics suitable for high-resolution hard x-ray nanoimaging. The 2D optics were assembled on microfabricated silicon templates with high orthogonality and lateral alignment precision, which were characterized using white-light interferometry and confirmed by x-ray measurements. The developed monolithic 2D MLL optics were successfully employed for hard x-ray nanofocusing and nanotomography experiments using the ptychography imaging modality, demonstrating sub-10 nm resolution in 2D and sample-limited ∼30 nm in three-dimensional while exhibiting excellent stability during extended measurements. The new 2D MLL templates with high alignment accuracy represent an important step forward in the development of 2D MLL optics toward direct nanoimaging experiments with sub-10 nm spatial resolution.

36 MATERIALS SCIENCE↗
DOE OSTI2012

NGC 5548: LACK OF A BROAD Fe K{alpha} LINE AND CONSTRAINTS ON THE LOCATION OF THE HARD X-RAY SOURCE

We present an analysis of the co-added and individual 0.7-40 keV spectra from seven Suzaku observations of the Sy 1.5 galaxy NGC 5548 taken over a period of eight weeks. We conclude that the source has a moderately ionized, three-zone warm absorber, a power-law continuum, and exhibits contributions from cold, distant reflection. Relativistic reflection signatures are not significantly detected in the co-added data, and we place an upper limit on the equivalent width of a relativistically broad Fe K{alpha} line at EW {<=} 26 eV at 90% confidence. Thus NGC 5548 can be labeled as a 'weak' type 1 active galactic nucleus (AGN) in terms of its observed inner disk reflection signatures, in contrast to sources with very broad, strong iron lines such as MCG-6-30-15, which are likely much fewer in number. We compare physical properties of NGC 5548 and MCG-6-30-15 that might explain this difference in their reflection properties. Though there is some evidence that NGC 5548 may harbor a truncated inner accretion disk, this evidence is inconclusive, so we also consider light bending of the hard X-ray continuum emission in order to explain the lack of relativistic reflection in our observation. If the absence of a broad Fe K{alpha} line is interpreted in the light-bending context, we conclude that the source of the hard X-ray continuum lies at radii r{sub s} {approx}> 100 r{sub g}. We note, however, that light-bending models must be expanded to include a broader range of physical parameter space in order to adequately explain the spectral and timing properties of average AGNs, rather than just those with strong, broad iron lines.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

IMPULSIVE PHASE CORONAL HARD X-RAY SOURCES IN AN X3.9 CLASS SOLAR FLARE

We present the analysis of a pair of unusually energetic coronal hard X-ray (HXR) sources detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager during the impulsive phase of an X3.9 class solar flare on 2003 November 3, which simultaneously shows two intense footpoint (FP) sources. A distinct loop top (LT) coronal source is detected up to {approx}150 keV and a second (upper) coronal source up to {approx}80 keV. These photon energies, which were not fully investigated in earlier analysis of this flare, are much higher than commonly observed in coronal sources and pose grave modeling challenges. The LT source in general appears higher in altitude with increasing energy and exhibits a more limited motion compared to the expansion of the thermal loop. The high-energy LT source shows an impulsive time profile and its nonthermal power-law spectrum exhibits soft-hard-soft evolution during the impulsive phase, similar to the FP sources. The upper coronal source exhibits an opposite spatial gradient and a similar spectral slope compared to the LT source. These properties are consistent with the model of stochastic acceleration of electrons by plasma waves or turbulence. However, the LT and FP spectral index difference (varying from {approx}0 to 1) is much smaller than commonly measured and than that expected from a simple stochastic acceleration model. Additional confinement or trapping mechanisms of high-energy electrons in the corona are required. Comprehensive modeling including both kinetic effects and the macroscopic flare structure may shed light on this behavior. These results highlight the importance of imaging spectroscopic observations of the LT and FP sources up to high energies in understanding electron acceleration in solar flares. Finally, we show that the electrons producing the upper coronal HXR source may very likely be responsible for the type III radio bursts at the decimetric/metric wavelength observed during the impulsive phase of this flare.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE ROLE OF INVERSE COMPTON SCATTERING IN SOLAR CORONAL HARD X-RAY AND {gamma}-RAY SOURCES

Coronal hard X-ray (HXR) and continuum {gamma}-ray sources associated with the impulsive phase of solar flares have been the subject of renewed interest in recent years. They have been interpreted in terms of thin-target, non-thermal bremsstrahlung emission. This interpretation has led to rather extreme physical requirements in some cases. For example, in one case, essentially all of the electrons in the source must be accelerated to non-thermal energies to account for the coronal HXR source. In other cases, the extremely hard photon spectra of the coronal continuum {gamma}-ray emission suggest that the low-energy cutoff of the electron energy distribution lies in the MeV energy range. Here, we consider the role of inverse Compton scattering (ICS) as an alternate emission mechanism in both the ultra- and mildly relativistic regimes. It is known that relativistic electrons are produced during powerful flares; these are capable of upscattering soft photospheric photons to HXR and {gamma}-ray energies. Previously overlooked is the fact that mildly relativistic electrons, generally produced in much greater numbers in flares of all sizes, can upscatter extreme-ultraviolet/soft X-ray photons to HXR energies. We also explore ICS on anisotropic electron distributions and show that the resulting emission can be significantly enhanced over an isotropic electron distribution for favorable viewing geometries. We briefly review results from bremsstrahlung emission and reconsider circumstances under which non-thermal bremsstrahlung or ICS would be favored. Finally, we consider a selection of coronal HXR and {gamma}-ray events and find that in some cases the ICS is a viable alternative emission mechanism.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PROSPECT OF STUDYING HARD X- AND GAMMA-RAYS FROM TYPE Ia SUPERNOVAE

We perform multi-dimensional, time-dependent radiation transfer simulations for hard X-ray and {gamma}-ray emissions, following radioactive decays of {sup 56}Ni and {sup 56}Co, for two-dimensional delayed-detonation models of Type Ia supernovae (SNe Ia). The synthetic spectra and light curves are compared with the sensitivities of current and future observatories for an exposure time of 10{sup 6} s. The non-detection of the {gamma}-ray signal from SN 2011fe at 6.4 Mpc by SPI on board INTEGRAL places an upper limit on the mass of {sup 56}Ni of {approx}< 1.0 M {sub Sun }, independently from observations in any other wavelengths. Signals from the newly formed radioactive species have not yet been convincingly measured from any SN Ia, but future X-ray and {gamma}-ray missions are expected to deepen the observable horizon to provide high energy emission data for a significant SN Ia sample. We predict that the hard X-ray detectors on board NuStar (launched in 2012) or ASTRO-H (scheduled for launch in 2014) will reach to SNe Ia at {approx}15 Mpc, i.e., one SN every few years. Furthermore, according to the present results, the soft {gamma}-ray detector on board ASTRO-H will be able to detect the 158 keV line emission up to {approx}25 Mpc, i.e., a few SNe Ia per year. Proposed next-generation {gamma}-ray missions, e.g., GRIPS, could reach to SNe Ia at {approx}20-35 Mpc by MeV observations. Those would provide new diagnostics and strong constraints on explosion models, detecting rather directly the main energy source of supernova light.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

TEMPORAL AND SPATIAL ANALYSES OF SPECTRAL INDICES OF NONTHERMAL EMISSIONS DERIVED FROM HARD X-RAYS AND MICROWAVES

We studied electron spectral indices of nonthermal emissions seen in hard X-rays (HXRs) and microwaves. We analyzed 12 flares observed by the Hard X-Ray Telescope aboard Yohkoh, Nobeyama Radio Polarimeters, and the Nobeyama Radioheliograph (NoRH), and compared the spectral indices derived from total fluxes of HXRs and microwaves. Except for four events, which have very soft HXR spectra suffering from the thermal component, these flares show a gap {Delta}{delta} between the electron spectral indices derived from HXRs {delta} {sub X} and those from microwaves {delta}{sub {mu}} ({Delta}{delta} = {delta} {sub X} - {delta}{sub {mu}}) of about 1.6. Furthermore, from the start to the peak times of the HXR bursts, the time profiles of the HXR spectral index {delta} {sub X} evolve synchronously with those of the microwave spectral index {delta}{sub {mu}}, keeping the constant gap. We also examined the spatially resolved distribution of the microwave spectral index by using NoRH data. The microwave spectral index {delta}{sub {mu}} tends to be larger, which means a softer spectrum, at HXR footpoint sources with stronger magnetic field than that at the loop tops. These results suggest that the electron spectra are bent at around several hundreds of keV, and become harder at the higher energy range that contributes the microwave gyrosynchrotron emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

EVIDENCE FOR A PHOTOSPHERIC COMPONENT IN THE PROMPT EMISSION OF THE SHORT GRB 120323A AND ITS EFFECTS ON THE GRB HARDNESS-LUMINOSITY RELATION

The short GRB 120323A had the highest flux ever detected with the Gamma-Ray Burst Monitor on board the Fermi Gamma-Ray Space Telescope. Here we study its remarkable spectral properties and their evolution using two spectral models: (1) a single emission component scenario, where the spectrum is modeled by the empirical Band function (a broken power law), and (2) a two-component scenario, where thermal (a Planck-like function) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the E{sub peak} of the event is unusually soft for a short gamma-ray burst (GRB; 70 keV compared to an average of 300 keV), while adding a thermal component leads to more typical short GRB values (E{sub peak} {approx} 300 keV). Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A based on (1) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (2) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, observed for the first time in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs (L{sub i}{sup Band} = (1.59 {+-} 0.84) x 10{sup 50} (E{sub peak,i}){sup 1.33{+-}0.07} erg s{sup -1}), which could be used as a possible redshift estimator for cosmology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

NuSTAR DETECTION OF HARD X-RAY PHASE LAGS FROM THE ACCRETING PULSAR GS 0834–430

The Nuclear Spectroscopic Telescope Array hard X-ray telescope observed the transient Be/X-ray binary GS 0834–430 during its 2012 outburst—the first active state of this system observed in the past 19 yr. We performed timing and spectral analysis and measured the X-ray spectrum between 3-79 keV with high statistical significance. We find the phase-averaged spectrum to be consistent with that observed in many other magnetized, accreting pulsars. We fail to detect cyclotron resonance scattering features that would allow us to constrain the pulsar's magnetic field in either phase-averaged or phase-resolved spectra. Timing analysis shows a clearly detected pulse period of ∼12.29 s in all energy bands. The pulse profiles show a strong, energy-dependent hard phase lag of up to 0.3 cycles in phase, or about 4 s. Such dramatic energy-dependent lags in the pulse profile have never before been reported in high-mass X-ray binary pulsars. Previously reported lags have been significantly smaller in phase and restricted to low energies (E < 10 keV). We investigate the possible mechanisms that might produce this energy-dependent pulse phase shift. We find the most likely explanation for this effect is a complex beam geometry.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Turbulent pitch-angle scattering and diffusive transport of hard X-ray-producing electrons in flaring coronal loops

Recent observations from RHESSI have revealed that the number of non-thermal electrons in the coronal part of a flaring loop can exceed the number of electrons required to explain the hard X-ray-emitting footpoints of the same flaring loop. Such sources cannot, therefore, be interpreted on the basis of the standard collisional transport model, in which electrons stream along the loop while losing their energy through collisions with the ambient plasma; additional physical processes, to either trap or scatter the energetic electrons, are required. Motivated by this and other observations that suggest that high-energy electrons are confined to the coronal region of the source, we consider turbulent pitch-angle scattering of fast electrons off low-frequency magnetic fluctuations as a confinement mechanism, modeled as a spatial diffusion parallel to the mean magnetic field. In general, turbulent scattering leads to a reduction of the collisional stopping distance of non-thermal electrons along the loop, and hence to an enhancement of the coronal hard X-ray source relative to the footpoints. The variation of source size L with electron energy E becomes weaker than the quadratic behavior pertinent to collisional transport, with the slope of L(E) depending directly on the mean free path λ associated with the non-collisional scattering mechanism. Comparing the predictions of the model with observations, we find that λ ∼ (10{sup 8}-10{sup 9}) cm for ∼30 keV, less than the length of a typical flaring loop and smaller than, or comparable to, the size of the electron acceleration region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Fast and Furious: Shock heated gas as the origin of spatially resolved hard X-ray emission in the central 5 kpc of the galaxy merger NGC 6240

We have obtained a deep, subarcsecond resolution X-ray image of the nuclear region of the luminous galaxy merger NGC 6240 with Chandra, which resolves the X-ray emission from the pair of active nuclei and the diffuse hot gas in great detail. We detect extended hard X-ray emission from kT ∼ 6 keV (∼70 MK) hot gas over a spatial scale of 5 kpc, indicating the presence of fast shocks with a velocity of ∼2200 km s{sup –1}. For the first time, we obtain the spatial distribution of this highly ionized gas emitting Fe XXV, which shows a remarkable correspondence to the large-scale morphology of H{sub 2}(1-0) S(1) line emission and Hα filaments. Propagation of fast shocks originating in the starburst-driven wind into the ambient dense gas can account for this morphological correspondence. With an observed L {sub 0.5-8} {sub keV} = 5.3 × 10{sup 41} erg s{sup –1}, the diffuse hard X-ray emission is ∼100 times more luminous than that observed in the classic starburst galaxy M82. Assuming a filling factor of 1% for the 70 MK temperature gas, we estimate its total mass (M {sub hot} = 1.8 × 10{sup 8} M {sub ☉}) and thermal energy (E {sub th} = 6.5 × 10{sup 57} erg). The total iron mass in the highly ionized plasma is M {sub Fe} = 4.6 × 10{sup 5} M {sub ☉}. Both the energetics and the iron mass in the hot gas are consistent with the expected injection from the supernovae explosion during the starburst that is commensurate with its high star formation rate. No evidence for fluorescent Fe I emission is found in the CO filament connecting the two nuclei.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The hard X-ray continuum of Cen a observed with INTEGRAL SPI

We revisit the average hard X-ray spectrum from the active galactic nucleus (AGN) of Centaurus A (Cen A) using 10 yr worth of observations with INTEGRAL SPI. This source has the highest flux observed from any AGNs in the SPI bandpass (23 keV-8 MeV). The 10 year light curve of Cen A is presented, and hardness ratios confirm that the spectral shape changes very little despite the luminosity varying by a factor of a few. Primarily, we establish the presence of a reflection component in the average spectrum by demonstrating an excess between 20 and 60 keV, from extending the spectral shape observed at low energy to the SPI regime. The excess in Chandra HETGS and INTEGRAL SPI data is well described by reflection of the dominant power-law spectrum from a neutral, optically thick atmosphere. We find that the reprocessed emission contributes 20%-25% of the 23-100 keV flux. The existence of a cutoff at tens to hundreds of kiloelectron volts remains controversial. Using simulated spectra, we demonstrate that a high energy cutoff reproduces the observed spectral properties of Cen A more readily than a simple power law. However, we also show that such a cutoff is probably underestimated when neglecting (even modest) reflection, and for Cen A would be at energies >700 keV, with a confidence of >95%. This is atypically high for thermal Comptonizing plasmas observed in AGNs, and we propose that we are in fact modeling the more gradual change in spectral shape expected of synchrotron self-Compton spectra.

79 ASTRONOMY AND ASTROPHYSICS↗