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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

High resolution X-ray scattering measurements for Advanced X-ray Astrophysics Facility /AXAF/

The Advanced X-ray Astrophysics Facility (AXAF) is to be an orbiting X-ray observatory with high resolution imaging capabilities. Specific goals of 0.5 arcsecond resolution, and an encircled energy of 60% within a 1.0 arcsecond diameter circle at 2.5 keV have been established for AXAF. Imaging X-ray optics are primarily limited by scattering of the X-rays from the mirror surfaces. To ensure that the AXAF goals can be met, comprehensive X-ray scattering measurements are being conducted on a large number of flat samples. Sub-arcsecond resolution is achieved in these measurements through use of the MSFC 1000 ft X-ray calibration facility and a high spatial resolution X-ray detector. Flats of various materials, various coatings, and a range of rms surface roughness are being evaluated. Direct evaluation of surface microroughness is also provided by a variety of optical and non-optical means. This paper describes the scattering measurement program, the instrumentation used to obtain the measurements and preliminary results of measurements on several of the sample flats.

Zombeck, M. V.↗
DOE OSTI2021

Anomalous X-Ray Scattering and Extended X-Ray Absorption Fine Structure Study of the Local Structure of CrFeCoNiMo x (x = 0.11, 0.18, and 0.23) High-Entropy Alloys

Anomalous x-ray scattering (AXS) and extended x-ray absorption fine structure (EXAFS) were used to determine the local structure of Mo in CrFeCoNiMo x (x = 0.11, 0.18, and 0.23), a high-entropy alloy with a face-centered cubic (FCC) lattice. No superlattice peaks were observed down to the 10 -4 intensity level. This observation along with the nearly constant decrease of the FCC diffraction peaks above the Mo K absorption edge suggests that Mo atoms have no preferred site occupancy in the FCC lattice. Modeling of the EXAFS data suggests a local chemical order in CrFeCoNiMo x , where in Mo-rich samples (e.g., x = 0.23), Mo atoms are preferably surrounded by lighter atoms, such as Cr.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Anthropogenic Influences on the Chemical and Mineral Composition in Pond Sediment by X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

Manmade detention ponds have historically been impacted by anthropogenic activities such as rainwater runoff, car emissions, and drainage from infrastructures, which can lead to complications for pond ecosystems. Sediment samples collected from the northern, southern, western, and eastern regions of a small pond on a suburban high school campus on Long Island, NY, were analyzed for potential chemical changes resulting from an inundation of water by a broken water main. Incorporating synchrotron X-ray techniques, sediment was analyzed using Submicron Resolution Spectroscopy, Tender Energy X-ray Spectroscopy, and X-ray Powder Diffraction to examine heavy metals, light elements, and minerals. Results include a Zn:Cu ratio increase from 4:1 to 10:1 in the eastern zone and a higher heavy metal presence in the western zone for all elements examined, with greater distribution throughout the pond post-inundation. Lighter elements appear to remain relatively unchanged. The appearance of diopside in the eastern zone post-inundation samples suggests contamination from the water main break, while the presence of carbonate minerals in the western zone is consistent with erosion of asphalt material from the adjacent parking lot.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1998

Hard X-ray Observation of Cygnus X-1 By the Marshall Imaging X-ray Experiment (MIXE2)

The second generation of the Marshall Imaging X-ray Experiment (MIXE2) was flown from Fort Sumner, New Mexico on May 7-8, 1997. The experiment consists of coded-aperture telescope with a field of view of 1.8 degrees (FWHM) and an angular resolution of 6.9 arcminutes. The detector is a large (7.84x10(exp 4) sq cm) effective area microstrip proportional counter filled with 2.0x10(exp5) Pascals of xenon with 2% isobutylene. We present MIXE2 observation of the 20-80keV spectrum and timing variability of Cygnus X-1 made during balloon flight.

Minamitani, Takahisa↗
NASA NTRS2006

Observations of Compact X-Ray Binaries with the Chandra X-Ray Observatory

The Chandra X-Ray Observatory Launched on July 23, 1999. The first X-ray photons were detected on August 12 of that same year. Subsequently observations with the Observatory, which features sub-arcsecond angular resolution, have revolutionized our understanding of the X-ray emitting sky providing hosts of spectacular energy-resolved images and high-resolution spectra. Here we present a brief overview of Chandra X-Ray Observatory observations of compact X-ray binaries.

Weisskopf, Martin C.↗
NASA NTRS1997

Testing the Pairs-Reflection Model with X-Ray Spectral Variability and X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects

This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to two successful ADP proposals to use archival Ginga and Rosat X-ray data for 'Testing the Pairs-Reflection model with X-Ray Spectral Variability' (in collaboration with Paola Grandi, now at the University of Rome) and 'X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects' (in collaboration with then-graduate student Rita Sambruna, now a post-doc at Goddard Space Flight Center). In addition, post-docs Joseph Pesce and Elena Pian, and graduate student Matthew O'Dowd, have worked on several aspects of these projects. The grant was originally awarded on 3/01/94; this report covers the full period, through May 1997. We have completed our project on the X-ray properties of radio-selected BL Lacs.

Urry, C. Megan↗
NASA NTRS1980

X-ray bursters and the X-ray sources of the galactic bulge

Type 1 X-ray bursts, optical, infrared, and radio properties of the galactic bulge sources, are discussed. It was proven that these burst sources are neutron stars in low mass, close binary stellar systems. Several burst sources are found in globular clusters with high central densities. Optical type 1 X-ray bursts were observed from three sources. Type 2 X-ray bursts, observed from the Rapid Burster, are due to an accretion instability which converts gravitational potential energy into heat and radiation, which makes them of a fundamentally different nature from Type 1 bursts.

Lewin, W. H. G.↗
NASA NTRS2005

[High-Performance Active Pixel X-Ray Sensors for X-Ray Astronomy]

The subject grants support development of High-Performance Active Pixel Sensors for X-ray Astronomy at the Massachusetts Institute of Technology (MIT) Center for Space Research and at MIT's Lincoln Laboratory. This memo reports our progress in the second year of the project, from April, 2004 through the present.

Bautz, Mark↗
NASA NTRS2012

Design and Tests of the Hard X-Ray Polarimeter X-Calibur

X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, and gamma-ray bursts. We designed, built and tested a hard X-ray polarimeter X-Calibur to be used in the focal plane of the InFOC(mu)S grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 10 - 80 keY X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of order unity.

Beilicke, M.↗
NASA NTRS2011

Design and Tests of the Hard X-Ray Polarimeter X-Calibur

X-ray polarimetry promises to give new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, and gamma-ray bursts. We designed, built and tested a hard X-ray polarimeter X-Calibur to be used in the focal plane of the InFOC(mu)S grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 10-80 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of order unity.

Beilicke, M.↗
NASA NTRS1974

Lunar elemental analysis obtained from the Apollo gamma-ray and X-ray remote sensing experiment

Gamma ray and X-ray spectrometers carried in the service module of the Apollo 15 and 16 spacecraft were employed for compositional mapping of the lunar surface. The measurements involved the observation of the intensity and characteristics energy distribution of gamma rays and X-rays emitted from the lunar surface. A large scale compositional map of over 10 percent of the lunar surface was obtained from an analysis of the observed spectra. The objective of the X-ray experiment was to measure the K spectral lines from Mg, Al, and Si. Spectra were obtained and the data were reduced to Al/Si and Mg/Si intensity ratios and ultimately to chemical ratios. The objective of the gamma-ray experiment was to measure the natural and cosmic ray induced activity emission spectrum. At this time, the elemental abundances for Th, U, K, Fe, Ti, Si, and O have been determined over a number of major lunar regions.

Trombka, J. I.↗
NASA NTRS1977

Lunar elemental analysis obtained from the Apollo gamma-ray and X-ray remote sensing experiment

Gamma-ray and X-ray spectrometers carried in the service modules of the Apollo 15 and Apollo 16 spacecraft were employed for compositional mapping of the lunar surface. The measurements involved the observation of the intensity and characteristic energy distribution of gamma rays and X-rays emitted from the lunar surface. A large-scale compositional map of over 10 percent of the lunar surface was obtained from an analysis of the observed spectra. The objective of the X-ray experiment was to measure the K spectral lines from Mg, Al, and Si. Spectra were obtained and the data were reduced to Al/Si and Mg/Si intensity ratios and ultimately to chemical ratios. Analyses of the results have indicated (1) that the Al/Si ratios are highest in the lunar highlands and considerably lower in the maria, and (2) that the Mg/Si concentrations generally show the opposite relationship. The objective of the gamma-ray experiment was to measure the natural and cosmic-ray-induced activity emission spectrum. At this time, the elemental abundances for Th, U, K, Fe, Ti, Si, and O have been determined over a number of major lunar regions. Regions of relatively high natural radioactivity were found in the Mare Imbrium and Oceanus Procellarum regions.

Trombka, J. I.↗
NASA NTRS2021

Wind suppression by X-rays in Cygnus X-3

Context: The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star. Aims: We aim to estimate how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3. Methods: We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott & Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. We solved the wind equations at different orbital angles from the line joining the stars and took the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We compared them to those obtained from observations. Results: We found that the ionization potentials of the ions contributing the most to the line force fall in the extreme-UV region(100–230 Å). If the flux in this region is high, the line force is weak, and consequently, the wind velocity is low. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping, this correlation disappears. We compared the XSTAR method used here with the comoving frame method and found that they agree reasonably well with each other. Conclusions. We show that soft X-rays in the extreme-UV region from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2–3) solar masses.

O. Vilhu↗
NASA NTRS1986

Development of high throughput X-ray telescopes for X-ray imaging and dispersive spectrometers

During the past year the technical approach to the realization of a high throughput Kirkpatrick-Baez X-ray mirror became better defined in terms of construction methodology and factors which affect maximum size. More progress was made than anticipated in the area of automatic figure formation. However, effort to improve the resolution of float glass by simple techniques were not successful. Mirror development, spectroscopy, all sky telescope, and explorer concept studies are discussed.

Gorenstein, P.↗
DOE OSTI2025

Linear and Nonlinear X-ray Spectra of Chiral Molecules: X-ray Circular Dichroism, Sum- and Difference-Frequency Generation of Fenchone and Cysteine

Recent advancements in X-ray light sources enable element-sensitive nonlinear spectroscopies for probing molecular chirality. We simulate X-ray absorption spectroscopy, X-ray circular dichroism (XCD), and nonlinear optical/X-ray SFG and DFG (OX SFG/DFG) signals for two prototypical chiral molecules, fenchone and cysteine. Furthermore, our multireference simulations reproduce experimental data and reveal how novel X-ray spectroscopies exploit the site- and element-sensitivity of X-rays to uncover molecular asymmetry. The XCD spectra show strong asymmetries at chiral centers, while distant atoms contribute weaker signals. The OX SFG/DFG signals, under fixed resonant optical excitation, strongly depend on the core and valence excitations. This allows us to introduce two-dimensional (2D) chirality-sensitive valence-core spectroscopy, which provides insight into the overlap between valence orbitals and local molecular asymmetry. Finally, our estimates using realistic laser and X-ray pulse parameters demonstrate that such nonlinear experiments are feasible at XFELs, offering a promising tool for investigating chiral molecules.

Circular dichroism spectroscopy↗
NASA NTRS1977

Optical candidates for two X-ray bursters and an X-ray pulsar

Faint blue stars are suggested as the optical counterparts of the X-ray bursters 4U (MXB) 1636-53 and 4U (MXB) 1735-44 as well as the 7-sec X-ray pulsar 4U 1626-67. The candidate stars have large UV excesses and were discovered well within the 20- and 30-arcsec error radii determined with the rotating modulation collimator aboard SAS 3. Photographic observations and photoelectric photometry of the candidate stars are discussed. It is shown that the candidates for 4U 1626-67 and 4U 1636-53 lie further from the reddened-supergiant or main sequence than any known X-ray source counterparts and have colors that are inconsistent with those of a reddened normal star, while the candidate for 4U 1735-44 has the colors of both Sco X-1 and a late O or BO star suffering about 1 mag of extinction.

Mcclintock, J. E.↗