Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “solar abundances”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

High-resolution X-ray spectroscopy of the supernova remnant N132D

A joint nonequilibrium ionization analysis of spectral data from the Einstein Observatory of the SNR N132D in the LMC is presented on the basis of data from the Focal Plane Crystal Spectrometer (FPCS) and the Solid State Spectrometer (SSS), and lower spectral resolution data from the IPC and the Monitor Proportional Counter (MPC). The FPCS detected individual emission lines of O VII, O VIII, Ne IX, Ne X, Fe XVII, and possibly Fe XX. Measured line widths for the oxygen lines suggest Doppler broadening that is roughly consistent with optically measured expansion velocities of 2250 km/s. At the SSS/IPC temperature, FPCS flux ratios constrain the O/Fe abundance to be at least 1.9 times its solar value and the O/Ne abundance to be 0.2-1.0 times its solar value. Models for remnants with progenitor masses of 20 and 25 solar masses are completely consistent with the data, while remnants with progenitor masses of 13 and 15 solar masses can be made consistent if the progenitors are required to eject a large fraction of their iron cores.

Hwang, Una↗
NASA NTRS1980

The interstellar medium on the Gamma Cassiopeiae line of sight

The interstellar medium on the Gamma Cas line of sight is studied through the observations of O I, H2, H I, D I, and Ar I absorption features with the Copernicus satellite. By using the velocity structure of the line of sight previously determined through atomic nitrogen, it is demonstrated that these neutrals are located in the same physical regions and that the O I and Ar I abundances could be solar, on the average, relative to N I in all components. The 1066.660 A Ar I line profile is contaminated by an unidentified line, already detected in the spectrum of Zeta Pup. Furthermore, a peculiar behavior of the Ar I abundance in the different components is reported, possibly associated with high-velocity interstellar gas present on the line of sight. It is concluded that the Gamma Cas line of sight could intercept a dense cloud which has been engulfed and disrupted by a shock.

Ferlet, R.↗
NASA NTRS1974

Solar particle events with anomalously large relative abundance of He-3

Experimental results are reported on three energetic particle events with extremely high abundance of He-3. The measurements were taken onboard the OGO-5 satellite. It was shown that the abundance of protons relative to He nuclei were significantly low in these events. Not more than four H-2 and three H-3 were detected during the entire period under study compared to 1110 H-3 nuclei. The limitations these observations place on theoretical models are discussed to explain He-3 flares.

Serlemitsos, A. T.↗
NASA NTRS1976

The abundances of zirconium and hafnium in the solar system

The concentrations of zirconium and hafnium have been determined in the Orgueil, Murchison, Allende, Bruderheim, and Alais meteorites by radiochemical neutron activation analysis. The mean Zr/Hf weight ratio in the first four of these meteorites is 31.3 (plus or minus 2.2), indicating no major fractionation of Zr from Hf. Alais contains anomalously high amounts of many refractory lithophile elements, including Zr and Hf. Orgueil contains 3.1 ppm Zr and 0.11 ppm Hf, corresponding to 9.0 and 0.16 atoms, respectively, relative to 1 million Si atoms.

Ganapathy, R.↗
DOE OSTI2020

Optoelectronic and material properties of solution-processed Earth-abundant Cu 2 BaSn(S, Se) 4 films for solar cell applications

Copper barium thioselenostannate, Cu 2 BaSnS 4-x Se x (CBTSSe), absorbers employ low-toxicity and abundant metals while offering low-cost manufacturing options, controllable stoichiometry and band gap tunability (from 2 eV at x = 0 to 1.55 eV at x = 3). CBTSSe can therefore be considered a prospective candidate for maintaining or improving upon the advantages of already commercialized Cu(In,Ga)(S,Se) 2 (CIGSSe) and CdTe absorbers. Here, we focus on solution-deposited stoichiometric CBTSSe films with band gap of 1.59 eV (x ≈ 3) and explore the fundamental film properties. Temperature- and excitation-dependent photoluminescence studies reveal a dominant defect emission at ~1.5 eV and a second deep defect feature at 1.15 eV. From time-resolved terahertz measurements, we find a charge carrier (electron and hole sum) mobility of ~140 cm 2 /Vs—i.e., comparable to values in CIGSSe or Cu 2 ZnSnS 4-x Se x (CZTSSe)—as well as a two-component minority carrier lifetime. A longer-lived lifetime component (~2 ns) arises from bulk recombination. However, strong recombination at the (bare) surface leads to a ~50 ps lifetime, inferior to state-of-the-art CIGSSe or CZTSSe absorbers. This recombination issue may worsen for CBTSSe/CdS interfaces, due to a cliff-like band alignment with 0.6 eV band offset, as revealed by ultraviolet photoemission spectroscopy. A low number of charge carriers within the absorber further contributes to a high series resistance. Employing these films, we also report the highest performance achieved from solution-processed trigonal CBTSSe thin-film photovoltaic devices, with open circuit voltage, short-circuit current density, fill factor and efficiency of 470 mV, 14.3 mA/cm 2 , 43.6% and 2.9%, respectively. The physical measurements provided on the stoichiometric solution-processed CBTSSe absorber further point to critical areas for future improvement of CBTSSe and related photovoltaic cells in the quest for higher efficiency devices based on earth abundant metals.

14 SOLAR ENERGY↗
NASA NTRS1991

First results from the Goddard High-Resolution Spectrograph - Element abundances as a function of velocity in the neutral gas toward Xi Persei

Observations of ultraviolet interstellar absorption lines toward Xi Persei obtained with the echelle mode of the Goddard High-Resolution Spectrograph (GHRS) aboard the HST at a resolution of 3.5 km/s are presented. The data for O I, C II, Mg II, S II, Fe II, Si II, Mn II, and Zn II are converted into representations of apparent column density per unit velocity, Na(v), over the velocity range from -30 to +40 km/s. The profiles for ions that are the dominant state of ionization in neutral clouds permit a study of the variation of element abundance with velocity caused by changes in the gas phase depletion in the different absorbing regions situated toward Xi Per. In the denser portions of the diffuse clouds, heavy element depletions are very large. However, in absorbing components near -5 and +25 km/s, the depletions are less severe, with a nearly solar gas phase abundance ratio being found for the gas in the +25 km/s component. The measurements confirm that the GHRS is well suited for diagnostic spectroscopy of interstellar gas.

Savage, Blair D.↗
NASA NTRS2006

Modeling Ellipsometry Measurements of Molecular Thin-Film Contamination on Genesis Array Samples

The discovery of a molecular thin-film contamination on Genesis flown array samples changed the course of preliminary assessment strategies. Analytical techniques developed to measure solar wind elemental abundances must now compensate for a thin-film contamination. Currently, this is done either by experimental cleaning before analyses or by depth-profiling techniques that bypass the surface contamination. Inside Johnson Space Center s Genesis dedicated ISO Class 4 (Class 10) cleanroom laboratory, the selection of collector array fragments allocated for solar wind analyses are based on the documentation of overall surface quality, visible surface particle contamination greater than 1 m, and the amount of thin film contamination measured by spectroscopic ellipsometry. Documenting the exact thickness, surface topography, and chemical composition of these contaminates is also critical for developing accurate cleaning methods. However, the first step in characterization of the molecular film is to develop accurate ellipsometry models that will determine an accurate thickness measurement of the contamination film.

Calaway, Michael J.↗
NASA NTRS1972

Enrichment of very heavy nuclei in the composition of solar accelerated particles.

Measurement of the abundances of the nuclei C, N, O, Ne, Mg, Si, Ar, and Ca and the group Cr-Co relative to oxygen from seven solar energetic-particle events in the energy range from about 14 to 61 MeV per nucleon with a solid-state detector telescope on the OGO-5 satellite, 1968-1971. The differential energy spectra of O (14 to 29 MeV per nucleon) and Cr-Co (3 to 61 MeV per nucleon) have a spectral index of about (-3) for a power law in kinetic energy. The relative abundances of C, N, O, and Ne are in excellent agreement with emulsion studies. However, when compared with the solar photospheric and coronal abundances, the OGO-5 measurements show a large enhancement of relative abundances beginning with Si, and extending to the Cr-Co group. The enhancement over the solar and universal abundances is in rough agreement with the composition of the galactic cosmic radiation.

Mogro-Campero, A.↗
NASA NTRS1989

Abundances of the elements in the intergalactic medium

A summary of the X-ray and optical spectroscopic data on emission lines from elements in clusters of galaxies is presented. The best data exists for Fe. For the about 30 well-observed clusters, the mean Fe abundance is about 0.4 solar, but there appears to be a real variation of at least a factor of 2. X-ray emission lines from O, Mg, Si and S have been detected, and their abundances are within a factor of a few of solar. Analysis of optical emission lines from cooling gas due to O, N, and S also indicates abundances not too far from solar values. The implications of the presence of heavy elements in the intergalactic medium of clusters for the evolution of the chemical abundances of galaxies are discussed.

Mushotzky, Richard↗
NASA NTRS1981

The isotopic composition of solar flare accelerated magnesium

Measurements of the abundances of three isotopes of magnesium in solar energetic particles are reported. Data were obtained from the Heavy Isotope Spectrometer Telescope on board the ISEE 3 spacecraft during a large solar particle event following the 2B solar flare of September 23, 1978. A two-dimensional maximum likelihood analysis of the mass determinations for each event, which were taken with a resolution of 0.23 amu, indicates a Mg-25/Mg-24 ratio of 0.14 (+0.05, -0.02) and a Mg-26/Mg-24 ratio of 0.15 (+0.04, -0.03) in the energy interval 12-36 MeV/n. The results are consistent with terrestrial magnesium isotope abundances.

Mewaldt, R. A.↗
NASA NTRS2012

Search for Large Presolar Silicate Grains in the QUE 99177 CR Chondrite

Silicates are among the most abundant pre-solar grain type, and their diverse chemical and isotopic compos-tions preserve detailed constraints on their stellar origins, condensation conditions, and nucleosynthetic and interstellar processes. Yet, owing to their small sizes, relatively few grains have been measured for isotopic compositions besides O and Si, and their mineralogy is poorly characterized. The average grain size (approx 270 nm) limits the number of analyses that can be conducted on a given grain, and their identification among solar system silicates introduces contaminating signal. These difficulties can be overcome by identifying large presolar silicate grains. However, such grains are very rare and only two approx 1 micron grains have been discovered. We are conducting a dedicated search for large presolar silicates in size-separated QUE 99177 matrix material. This primitive meteorite has among the highest abundance of presolar silicates

Nguyen, A. N.↗
NASA NTRS2008

The Helium Abundance at Quiescent Current Sheets and the Slow Solar Wind

Ulysses MAG data were used to identify current sheets during sunspot minimum years of 1994-1997 and 2004-2006. The purpose of limiting the dates was to focus attention on 'quiescent current sheets' with as little influence from ICMEs as possible. SWOOPS data were then used in a superposed epoch analysis to study Helium abundance in the vicinity of the current sheet, similar to the study done by Borrini et al. (1981). That earlier study found a narrow (ca. 2 day) minimum in He/H around the current sheet that is extremely variable from one year to the next in the period 1971-1978. A similar result is found here for data at all latitudes and distances in 2004-2006. Conversely, data from 1994-1997 produce a deep minimum several times wider (ca. 10 days). The reason for this is found to be that low He/H is more closely associated with slow wind than the current sheet per se. There are thus apparently at least two sources of slow wind, one associated with very low He/H of 0-0.02 and one associated with moderate abundance of 0.03-0.05. The large variability is a consequence of the relatively small number of current sheet encounters around solar minimum and the random distribution of low He/H intervals, lasting less than 1 day to more than 7 days, throughout slow wind.

Suess, Steven T.↗
NASA NTRS1974

On the e-process - Its components and their neutron excesses

The pattern of abundances within the iron-abundance peak of the solar system is analyzed for various Cr, Fe, and Ni abundances, and a method is developed for finding the best fit to a given set of abundances with a chosen number of zones, i.e., mass contributions characterized by differing values of eta. This material can be synthesized by a superposition of e-process compositions in a low-eta region (eta = 0.003) and a high-eta region (eta = 0.065 -0.080) with at least 85% coming from the low-eta region. Addition of a third eta zone is unproductive. The applicability of the particle-poor freeze out is discussed in the light of these abundances, and the results of employing different numbers and types of zones are interpreted as an indication of the relative abundances themselves. Ejection of the low-eta zones is of great interest in gamma-ray astronomy and for empirical testing of theories of nucleosynthesis. The distribution of high zones should give important information about the formation of collapsed remnants.

Hainebach, K. L.↗
NASA NTRS1979

Cosmic-ray abundances of individual elements in the Z interval between 26 and 30

The relative abundances of Fe, Co, Ni, Cu, and Zn in the cosmic rays have been measured using a large-area balloon-borne electronic detector system. The abundance ratios Ni/Fe and Zn/Fe are 5.0 + or - 0.2% and 0.06 + or - 0.01%, respectively. The Zn abundance is low (40%) compared with the Cameron (1973) (C1) solar system, and is best consistent with the solar system C2 meteorite abundances. The ratios Co/Fe and Cu/Fe, extrapolated to the top of the atmosphere, are 0.68 + or - 0.14% and 0.066 + or - 0.030% respectively; since charge peaks are not resolved at Co and Cu, these results are taken as upper limits of 0.8% and 0.1%, respectively. The Co upper limit is consistent with complete decay of Co-57 at the source and implies a lower limit of 2 years for the time between nucleosynthesis and acceleration of these nuclei.

Tueller, J.↗
NASA NTRS1987

Could icy impacts reconcile Venus with Earth and Mars

The problem of volatile sources in the martian atomosphere was studied. It is suggested that a combination of an impact by an icy planetesimal (radius about 150 km) and solar wind implantation of neon could explain the noble gas abundances on Venus. Early solar wind would supply the right amount of neon with the correct Ne-20/Ne-22 as compared with lunar soils. However, observations of noble gases in a fresh comet are needed to test this hypothesis.

Owen, T.↗
NASA NTRS2012

Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

Primitive Solar System materials (e.g. chondrites. IDPs, the Stardust sample) show large variations in isotopic composition of the major volatiles (H, C, N, and O ) even within samples, witnessing to various degrees of processing in the protosolar nebula. For ex~ ample. the very pronounced D enhancements observed in IDPs [I] . are only generated in the cold. dense component of the interstellar medium (ISM), or protoplanetary disks, through ion-molecule reactions in the presence of interstellar dust. If this isotopic anomaly has an interstellar origin, this leaves open the possibility for preservation of other isotopic signatures throughout the form ation of the Solar System. The most common form of carbon in the ISM is CO molecules, and there are two potential sources of C-13 fractionation in this reservoir: low temperature chemistry and selective photodissociation. While gas-phase chemistry in cold interstellar clouds preferentially incorporates C-13 into CO [2], the effect of self-shielding in the presence of UV radiation instead leads to a relative enhancement of the more abundant isotopologue, 12CO. Solar System organic material exhibit rather small fluctuations in delta C-13 as compared to delta N-15 and delta D [3][1], the reason for which is still unclear. However, the fact that both C-13 depleted and enhanced material exists could indicate an interstellar origin where the two fractionation processes have both played a part. Formaldehyde (H2CO) is observed in the gas-phase in a wide range of interstellar environments, as well as in cometary comae. It is proposed as an important reactant in the formation of more complex organic molecules in the heated environments around young stars, and formaldehyde polymers have been suggested as the common origin of chondritic insoluable organic matter (IOM) and cometary refractory organic solids [4]. The relatively high gas-phase abundance of H2CO observed in molecular clouds (10(exp- 9) - 10(exp- 8) relative to H2) makes it feasible to observe its less common isotopologues. As a step in our investigation of C-13 fractionation patterns in the ISM, we here present comparisons between observations of the C-13 fraction in formaldehyde, and chemical fractionation models.

Wirstrom, E. S.↗