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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Atomic data from the iron project. 3: Rate coefficients for electron impact excitation of boron-like ions: Ne VI, Mg VIII, Al IX, Si X, S XII, Ar XIV, Ca XVI and Fe XXII

Collison strengths and maxwellian averaged rate coefficients have been calculated for the 105 transitions among all 15 fine structure levels of the 8 LS terms 2s(sup 2) 2 P(P-2(sup 0 sub 1/, 3/2)), 2s2p(sup 2)(P-4(sub 1/2,3/2,5/2), D-2(sub 3/2, 5/2), S-2(sub 1/2), P-2(sub 1/2, 3/2)), 2p(sup 3)(S-4(sup 0)(sub 3/2), D-2(sup 0 sub 3/2, 5/2), P-2(sup 0 sub 1/2, 3/2)) in highly- charged B-like Ne, Mg, Al, Si, S, Ar, Ca and Fe. Rate coefficients have been tabulated at a wide range of temperatures, depending on the ion charge and abundance in plasma sources. Earlier work for O IV has also been extended to include the high temperature range. A brief discussion of the calculations, sample results, and comparison with earlier works is also given. While much of the new data should be applicable to UV spectral diagnostics, the new rates for the important ground state fine structure transition P-2(sup 0 sub 1/2)-P-2(sup 0 sub 3/2) should result in significant revision of the IR cooling rates in plasmas where B-like ions are prominent constituents, since the new rate coefficients are generally higher by several factors compared with the older data.

Zhang, Hong Lin↗
NASA NTRS2001

Ratio of Sodium to Potassium in the Mercurian Exosphere

Sodium (Na) and Potassium (K) atoms can be seen in the exosphere of Mercury and the Moon because they are extremely efficient at scattering sunlight. These species must be derived from surface materials, so that we might expect the ratio of sodium to potassium to reflect the ratio of these elements in the surface crust. This expectation is approximately born out for the Moon, where the ratio of sodium to potassium in the lunar exosphere averages to be about 6, not too far from the ratio in lunar rocks of 2 to 7. However, the ratio in the Mercury exosphere was found to be in the range 80 to 190, and at least once, as high as 400. The sodium and potassium atoms seen in the Mercury exosphere represent a balance between production from the surface and loss to space. Only if the production efficiencies and loss rates for Na and K were equal, would the ratio of Na to K in the exosphere reflect the ratio in the surface rocks. Since a value of 100 or more for the ratio of sodium to potassium in the surface rocks seems very unlikely, the high values of the observed ratios suggests that either production efficiencies or loss processes for the two elements are not equivalent. It does not seem likely that source processes should be different on the Moon and Mercury by an order of magnitude. This suggests that loss processes rather than source processes are the cause of the difference between the two. The major loss processes for sodium and potassium on Mercury are radiation pressure and trapping of photoions by the solar wind. Radiation pressure can reach 50-70% of surface gravity, and can sweep sodium and potassium atoms off the planet, provided they are sufficiently hot. Photoionization followed by trapping of the ions in the solar wind is the other major loss process. Photoions are accelerated to keV energies in the magnetosphere, and may either intercept the magnetopause, and be lost from the planet, or impact the planetary surface. Ions that impact the surface are neutralized, and are then available for resupply to the exosphere. The loss efficiency depends on characteristics of the magnetosphere that determine the fraction of the ions that are recycled by neutralization on the surface. Over the preceding decade, we have collected sodium and potassium data for Mercury at irregular intervals. We analyzed these data to extract values for the Na/K ratio at a variety of conditions on Mercury. Additional information is contained in the original extended abstract.

Potter, A. E.↗
NASA NTRS1991

Cross sections for direct and dissociative ionization of NH3 and CS2 by electron impact

A crossed electron beam-molecular beam collision geometry is used to measure cross sections for the production of positive ions by electron impact on NH3 and CS2. Ionization cross-section data for NH3 and the values of various cross sections are presented, as well as ionization efficiency curves for CS2. Considerable differences are found between the various results on NH3. The present values are close to the data of Djuric et al. (1981). The semiempirical calculations of Hare and Meath (1987) differ considerably in the absolute values of cross sections. Discrepancies were observed in comparisons of cross sections of other fragment ions resulting from the ionization and dissociate ionization of NH3.

Rao, M. V. V. S.↗
NASA NTRS1988

Effect of mid-altitude ion heating on ion outflow at polar latitudes

The effect of ion heating on polar ion outflow, when either the parallel or perpendicular (or both) ion temperatures at the exobase are elevated above values typical for the ionosphere, was investigated using a modified semikinetic steady-state model of Barakat and Schunk (1983) that allowed for anisotropic ion heating at the exobase and eliminated lower boundary potential jumps. In addition, the relative impact of the ion heating vs electron heating on the oxygen escape fluxes was investigated by examining the flux of O(+) ions for various combinations of electron and ion temperatures. It is demonstrated that the O(+) escape flux can be increased, to levels as high as were obtained by Barakat and Schunk (1983) with the electron temperatures of 10,000 K, by raising, instead, the ion temperatures (but to values considerably less than the 100,000 K observed by Moore et al., 1986).

Li, Peng↗
NASA NTRS1997

Description and Analysis of Core Samples: The Lunar Experience

Although no samples yet have been returned from a comet, extensive experience from sampling another solar system body, the Moon, does exist. While, in overall structure, composition, and physical properties the Moon bears little resemblance to what is expected for a comet, sampling the Moon has provided some basic lessons in how to do things which may be equally applicable to cometary samples. In particular, an extensive series of core samples has been taken on the Moon, and coring is the best way to sample a comet in three dimensions. Data from cores taken at 24 Apollo collection stations and 3 Luna sites have been used to provide insight into the evolution of the lunar regolith. It is now well understood that this regolith is very complex and reflects gardening (stirring of grains by micrometeorites), erosion (from impacts and solar wind sputtering), maturation (exposure on the bare lunar surface to solar winds ions and micrometeorite impacts) and comminution of coarse grains into finer grains, blanket deposition of coarse-grained layers, and other processes. All of these processes have been documented in cores. While a cometary regolith should not be expected to parallel in detail the lunar regolith, it is possible that the upper part of a cometary regolith may include textural, mineralogical, and chemical features which reflect the original accretion of the comet, including a form of gardening. Differences in relative velocities and gravitational attraction no doubt made this accretionary gardening qualitatively much different than the lunar version. Furthermore, at least some comets, depending on their orbits, have been subjected to impacts of the uppermost surface by small projectiles at some time in their history. Consequently, a more recent post-accretional gardening may have occurred. Finally, for comets which approach the sun, large scale erosion may have occurred driven by gas loss. The uppermost material of these comets may reflect some of the features of this erosional process, such as crust formation, and variations with depth might be expected. Overall, the upper few meters of a comet may be as complex in their own way as the upper few meters of the lunar regolith have proven to be, and by analogy, detailed studies of core samples containing this depth information will be needed to understand these processes and the details of the accretional history and the subsequent alteration history of comets.

McKay, David S.↗
NASA NTRS1981

Negative ions in the ionospheres of planetary bodies without atmospheres

It is noted that negative ions may be formed in the ionospheres of Mercury, the moon, and Jupiter's satellites with densities of a few percent of the ionospheric electron density. Negative ions result from three mechanisms at the planetary surface: charge inversion during energetic proton scattering, with simultaneous secondary negative ion emission, and micrometeorite impacts. The density and distribution of negative ions around planetary bodies depends primarily on the negative ion lifetimes determined through photodetachment by solar radiation.

Wekhof, A.↗
NASA NTRS1980

Interference with negative particle sampling due to formation of positive ions in a quadrupole mass spectrometer

A quadrupole mass spectrometer has been utilized to study active discharges containing Cs vapor. Production of positive ions by electron impact within the mass spectrometer and subsequent secondary electron emission from cesiated surfaces produced spurious or pseudonegative ion signals which interfered with attempts to sample negative ions from the plasma. These effects may also occur in other gas discharge systems.

Kuehn, D. G.↗
NASA NTRS2011

Lunar Ion Transport Near Magnetic Anomalies: Possible Implications for Swirl Formation

The bright swirling features on the lunar surface in areas around the Moon but most prominently at Reiner Gamma, have intrigued scientists for many years. After Apollo and later Lunar Prospector (LP} mapped the Lunar magnetic fields from orbit, it was observed that these features are generally associated with crustal magnetic anomalies. This led researchers to propose a number of explanations for the swirls that invoke these fields. Prominent among these include magnetic shielding in the form of a mini-magnetosphere which impedes space weathering by the solar wind, magnetically controlled dust transport, and cometary or asteroidal impacts that would result in shock magnetization with concomitant formation ofthe swirls. In this presentation, we will consider another possibility, that the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. In this scenario, ions that are created in these impacts are under the influence of these fields and can drift for significant distances before encountering the magnetic anomalies when their trajectories are disrupted and concentrated onto nearby areas. These ions may then be responsible for chemical alteration of the surface leading either to a brightening effect or a disruption of space weathering processes. To test this hypothesis we have run ion trajectory simulations that show ions from regions about the magnetic anomalies can be channeled into very small areas near the anomalies and although questions remain as to nature of the mechanisms that could lead to brightening of the surface it appears that the channeling effect is consistent with the existence of the swirls.

Keller, J. W.↗
NASA NTRS1978

Field ionization kinetic and electron impact studies of gas phase transition states - The cyclic bromonium ion

Cis- and trans-isomers of 4-t-butylcyclohexyl bromide were studied to determine the mechanism of cyclic bromonium ion formation. The field ionization kinetic and electron impact data indicate that the formation of the cyclic structure occurs simultaneously with loss of the neutral fragment. The data also show that little or no gas-phase cis-trans isomerization occurs.

Green, M. M.↗
NASA NTRS2013

Jovian Plasmas Torus Interaction with Europa. Plasma Wake Structure and Effect of Inductive Magnetic Field: 3D Hybrid Kinetic Simulation

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with Oþ þ and Sþ þ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive magnetic dipole and low oceanic shell conductivity).

Jovian magnetosphere↗
DOE OSTI2025

Impact of Module Configuration on Lithium-Ion Battery Performance and Degradation: Part I. Energy Throughput, Voltage Spread, and Current Distribution

Batteries are commonly connected in series and parallel to create modules that fulfill the power and energy requirements of specific applications. However, conclusions about battery performance and degradation under different conditions, as well as predictive models, are often derived from single cell cycling results. In this study, we evaluate the performance of six different series-parallel configurations of commercial lithium nickel manganese cobalt cells over hundreds of cycles. Each cell within the modules was individually instrumented for voltage, current, and temperature monitoring. We quantified the impact of module configuration on overall energy throughput, the voltage spread among series-connected cells, and the current heterogeneity in parallel-connected cells. This module cycling study, one of the broadest reported to date, supports systematic evaluation of the performance trade-offs, pack penalty, and safety implications of different module configurations.

25 ENERGY STORAGE↗
NASA NTRS1996

Effects of track structure and cell inactivation on the calculation of heavy ion mutation rates in mammalian cells

It has long been suggested that inactivation severely effects the probability of mutation by heavy ions in mammalian cells. Heavy ions have observed cross sections of inactivation that approach and sometimes exceed the geometric size of the cell nucleus in mammalian cells. In the track structure model of Katz the inactivation cross section is found by summing an inactivation probability over all impact parameters from the ion to the sensitive sites within the cell nucleus. The inactivation probability is evaluated using the dose-response of the system to gamma-rays and the radial dose of the ions and may be equal to unity at small impact parameters for some ions. We show how the effects of inactivation may be taken into account in the evaluation of the mutation cross sections from heavy ions in the track structure model through correlation of sites for gene mutation and cell inactivation. The model is fit to available data for HPRT mutations in Chinese hamster cells and good agreement is found. The resulting calculations qualitatively show that mutation cross sections for heavy ions display minima at velocities where inactivation cross sections display maxima. Also, calculations show the high probability of mutation by relativistic heavy ions due to the radial extension of ions track from delta-rays in agreement with the microlesion concept. The effects of inactivation on mutations rates make it very unlikely that a single parameter such as LET or Z*2/beta(2) can be used to specify radiation quality for heavy ion bombardment.

NASA Discipline Number 45-10↗
NASA NTRS1994

Physical and Tribological Characteristics of Ion-Implanted Diamond Films

Unidirectional sliding friction experiments were conducted with a natural, polished diamond pin in contact with both as-deposited and carbon-ion-implanted diamond films in ultrahigh vacuum. Diamond films were deposited on silicon, silicon carbide, and silicon nitride by microwave-plasma-assisted chemical vapor deposition. The as-deposited diamond films were impacted with carbon ions at an accelerating energy of 60 keV and a current density of 50 micron A/cm(exp 2) for approximately 6 min, resulting in a dose of 1.2 x 10(exp 17) carbon ions/cm(exp 2). The results indicate that the carbon ion implantation produced a thin surface layer of amorphous, nondiamond carbon. The nondiamond carbon greatly decreased both friction and wear of the diamond films. The coefficients of friction for the carbon-ion-implanted, fine-grain diamond films were less than 0.1, factors of 20 to 30 lower than those for the as-deposited, fine-grain diamond films. The coefficients of friction for the carbon-ion-implanted, coarse-grain diamond films were approximately 0.35, a factor of five lower than those for the as-deposited, coarse-grain diamond films. The wear rates for the carbon-ion-implanted, diamond films were on the order of 10(exp -6) mm(exp 3)/Nm, factors of 30 to 80 lower than that for the as-deposited diamond films, regardless of grain size. The friction of the carbon-ion-implanted diamond films was greatly reduced because the amorphous, nondiamond carbon, which had a low shear strength, was restricted to the surface layers (less than 0.1 micron thick) and because the underlying diamond materials retained their high hardness. In conclusion, the carbon-ion-implanted, fine-grain diamond films can be used effectively as wear resistant, self-lubricating coatings for ceramics, such as silicon nitride and silicon carbide, in ultrahigh vacuum.

Miyoshi, K.↗
NASA NTRS2011

The Plasma Environment at Mercury

Mercury is the least explored terrestrial planet, and the one subjected to the highest flux of solar radiation in the heliosphere. Its highly dynamic, miniature magnetosphere contains ions from the exosphere and solar wind, and at times may allow solar wind ions to directly impact the planet's surface. Together these features create a plasma environment that shares many features with, but is nonetheless very different from, that of Earth. The first in situ measurements of plasma ions in the Mercury space environment were made only recently, by the Fast Imaging Plasma Spectrometer (FIPS) during the MESSENGER spacecraft's three flybys of the planet in 2008-2009 as the probe was en route to insertion into orbit about Mercury earlier this year. Here. we present analysis of flyby and early orbital mission data with novel techniques that address the particular challenges inherent in these measurements. First. spacecraft structures and sensor orientation limit the FIPS field of view and allow only partial sampling of velocity distribution functions. We use a software model of FIPS sampling in velocity space to explore these effects and recover bulk parameters under certain assumptions. Second, the low densities found in the Mercury magnetosphere result in a relatively low signal-to-noise ratio for many ions. To address this issue, we apply a kernel density spread function to guide removal of background counts according to a background-signature probability map. We then assign individual counts to particular ion species with a time-of-flight forward model, taking into account energy losses in the carbon foil and other physical behavior of ions within the instrument. Using these methods, we have derived bulk plasma properties and heavy ion composition and evaluated them in the context of the Mercury magnetosphere.

Raines, James M.↗
DOE OSTI2025

Microstructure Scale Lithium-Ion Battery Modeling: Part I. On Through-Plane Heterogeneity, Impact of Mesh Representation, and Differences between Macro- and Microscale Models

Li-ion battery performance and degradation are strongly correlated with the electrode microstructures and can be modeled at different scales, each with their own limitations. Herein, we compare predictions achieved with a macro- and a micro-scale model, that is, respectively, neglecting or considering the microstructural heterogeneity of the composite electrodes, on virtual numerically generated and real microstructures. While both models are in relative agreement at the low charge rates, differences arise for fast charging scenarios and especially for the real, highly heterogenous, microstructures. The microscale model predicts that electrolyte concentration saturation and depletion, respectively, at the back of the cathode and of the anode are exacerbated, and that lithium plating occurs earlier for real microstructures. The present work also indicates that the mesh representation significantly impacts the microscale model predictions, and consequently that microscale models should add surface area as a parameter to consider explicitly surface roughness. This article is the first of a series, with subsequent entries further investigating in-plane heterogeneities, lithium plating, and the impact of microstructure representativity on model predictions.

25 ENERGY STORAGE↗
NASA NTRS1983

Energetic atomic and molecular ions in Saturn's magnetosphere

Voyager 1 and 2 sensor data are analyzed in order to derive the composition, energy spectra, and spatial distribution of energetic ions in the Saturn magnetosphere. In order of abundance, the major species are H, H2(+), He, H3(+), C, and O. The fluxes of all species decreased inside the orbit of Dione, and nearly vanished in the 'slot' region within the orbit of Tethys. Both satellite absorption and precipitation due to pitch angle scattering may be important loss processes in that region. In the outer magnetosphere, photodissociation rapidly destroys a large fraction of the H2(+) ions, but dissociation by impact with neutral H atoms is faster for H2(+) ions in the lowest vibrational state. The ground state lifetime of about 23 days places a limit of about 10-100 days on the mean overall residence time for energetic ions in Saturn's magnetosphere.

Hamilton, D. C.↗
NASA NTRS1993

Radiative lifetimes of the 2s2p2(4P) metastable levels of N III

The radiative decay rates of N III 175 nm intersystem lines were measured in the laboratory by recording the time dependence of photon intensities emitted as the 2s2p2(4P) metastable term of N(2+) ions decay to the 2s22p(2P0) ground term. A cylindrical radio frequency ion trap was used to store the electron impact-produced N(2+) ions. The radiative decay signals were analyzed by multiexponential least-squares fits to the data. The measured radiative decay rates to the ground term are 1019(+/- 64)/s for 4P sub 1/2, 74.5(+/- 5.4)/s for 4P sub 3/2, and 308( +/- 22)/s for 4P sub 5/2. Comparisons of the measured values with theoretical values are presented.

Fang, Z.↗