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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Solar wind iron charge states preceding a driver plasma

Iron and silicon/sulfur charge state and velocity measurements and iron density measurements in the shocked solar wind which preceded the flare-related driver plasma observed on September 29, 1978 by ISEE 3 are reported. Given the assumption that the driver plasma is magnetically isolated from the ambient solar wind, the contact surface separating these two plasma regimes is expected to form an distinct boundary in the charge state composition. Instead, an apparent transition in the ionization state of the shocked solar wind from ambient solar wind values to those typical of the driver plasma is observed. This result may reflect X-ray ionization of the solar wind plasma near the flare site.

Galvin, A. B.↗
NASA NTRS1993

The reionization of the universe: The feedback of galaxy formation on the intergalactic medium

The thermal and ionization evolution of a uniform intergalactic medium (IGM) composed of H and He, undergoing reionization, including the mean effect of gas clumps embedded in a smoothly distributed ambient gas were calculated. The rate equations for ionization and recombination were solved together with the equations of energy conservation, including the effects of cosmological expansion, radiative and Compton cooling, and the diffuse flux emitted by the gas, and radiative transfer. The contribution to the continuum opacity of the universe due to the observed quasar absorption line clouds (QALC'S) were included. A variety of sources of photoionization, including quasars and primeval galaxies, as well as the possibility that hydrodynamical processes deposit thermal energy in the IGM were considered. Applications of these calculations including the evolution of the Ly-alpha forest clouds are described. A self-consistent treatment of the thermal and ionization history of the intergalactic medium (IGM) must take account of the growth of structure in the universe, since the mean density of the IGM corresponds primarily to the time-varying uncollapsed fraction of the baryon-electron component of the matter, and the collapsed fraction, in turn, can have a feedback effect on this uncollapsed fraction by releasing ionizing radiation and thermal energy and by contributing to the opacity of the universe. The coupled evolution of the IGM and the emerging structure with a special focus on the reionization of the IGM, which is believed to have been completed by some redshift z is approximately greater than 4, as inferred from the absence of the Gunn-Peterson effect in the spectra of high z quasars, are studied. The results and implications of detailed, numerical calculations of the thermal and ionization balance and radiative transfer in a uniform IGM of H and He, including the mean effect of an evolving distribution of gas clumps embedded in a smoothly distributed ambient gas is described.

Shapiro, Paul R.↗
NASA NTRS1990

Non-solar UV produced ions observed optically from the 'Crit I' critical velocity ionization experiment

A critical velocity ionization experiment was carried out with a heavily instrumented rocket launched from Wallops Island on May 13, 1986. Two neutral barium beams were created by explosive shaped charges released from the rocket and detonated at 48 deg to B at altitudes near 400 km and below the solar UV cutoff. Critical velocity ionization was expected to form a detectable ion jet along the release field line, but, instead, an ion cloud of fairly uniform intensity was observed stretching from the release field line across to where the neutral barium jet reached sunlight. The process creating these ions must have been present from the time of the release; the efficiency is estimated to be equivalent to an ionization time constant of 1800 sec. This ionization is most likely from collisions between the neutral barium jet and the ambient atmospheric oxygen, and, if so, the cross section for collisional ionization is 9 x 10 to the -18th sq cm.

Stenbaek-Nielsen, H. C.↗
NASA NTRS2015

The Time-Dependent Chemistry of Cometary Debris in the Solar Corona

Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.

sun: corona↗
NASA NTRS2001

Meteoric Ions in Planetary Ionospheres

Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

Pesnell, W. D.↗
NASA NTRS1976

The penetration of soft electrons into the ionosphere

Calculations are presented of energy spectra and angular and spatial distributions of electron fluxes in the ionosphere resulting from precipitation of monoenergetic (E = 25, 50, and 100 eV) electrons. The incident electrons are assumed to be isotropic over the downward direction. It is found that the resulting steady-state electron fluxes above ca. 300 km are highly anisotropic and that the pitch-angle distribution is energy dependent. About 15% of the incident electrons are backscattered elastically to the protonosphere. A much larger number of electrons escapes after they have deposited part of their energy in the atmosphere. The mean energy of the escaping electrons is about half that of the incident electrons. About 50% of the incident energy is absorbed in the atmosphere, the remainder being returned to the protonosphere. The rate of energy absorption is a maximum at heights between 300 and 400 km. Most of the energy is absorbed in ionization and excitation of atomic oxygen; an appreciable amount is absorbed as heat by the ambient electron gas. Altitude profiles are presented for the rates of ionization, excitation, and electron heating caused by soft-electron precipitation.

Mantas, G. P.↗
DOE OSTI2022

Resolving Graphite‐Electrolyte Interphase of Lithium‐Ion Batteries using Air‐Tight Ambient Mass Spectrometry

Abstract The formation of a stable solid electrolyte interphase (SEI) at graphite electrode is necessary for lithium‐ion batteries (LIB) to prevent excessive degradation of electrolytes. Until now, the exact organic composition of SEI has not been decisively determined with lithium ethylene mono‐carbonate (LEMC) being one of the debated components. An air‐tight ambient mass spectrometry (MS) platform is developed to directly characterize the air‐sensitive organic components present in SEI. Ionization occurs via a solvent‐free field‐induced process at atmospheric pressure. Our experimental data, based on tandem MS analysis, revealed LEMC to be the major organic component in SEI. This result resolves a long‐standing mystery surrounding the composition of native SEI in LIB, where no trace of the other debated compound, lithium ethylene dicarbonate, was detected. The energetics of fragmentation of LEMC and the corresponding stabilities of various ionic species detected during the air‐tight ambient MS analysis were calculated using density functional theory (DFT). Our findings confirmed favorable protonation energies and suggested the molecular structures for many of the detected species. Solvent (i. e., ethylene carbonate)‐induced stabilization effects observed during the ionization process were also confirmed by DFT. The reported study encourages the routine use of ambient mass spectrometry to characterize both anodic and cathodic electrodes of all battery types as well as to study other air‐sensitive materials in their native state.

25 ENERGY STORAGE↗
NASA NTRS1972

Measurements of the UV and VUV transmission of optical materials during high energy electron irradiation

An experimental program was conducted in which the optical transmission of several transparent materials was measured during high energy electron irradiation. These experiments were conducted using the Dynamitron electron accelerator as a continuous source of 1.5 MeV electrons and the LINAC electron accelerator as a pulsed source of 5-7 MeV electrons. The experimental program consisted of three major portions. The first portion, the optical transmission of fused silica, BeO, MgF2, and LiF was measured at vacuum ultraviolet wavelengths in the range 1550-2000 A during ambient temperature, 1.5 MeV electron irradiation at ionizing dose rates to 0.5 Mrad/sec. In the second portion of the program, the optical transmission of fused silica and BeO was measured in the range 2000-3000 A during high dose rate, elevated temperature 1.5 MeV electron irradiation. In particular, accurate measurements of the optical transmission were made at ionizing dose rates as high as 10 Mrad/sec. In the final portion of the program, the optical transmission of fused silica and BeO was measured in the wavelength range 2000-3000 A during pulsed 5 and 7 MeV electron irradiation from the LINAC accelerator. The maximum time averaged ionizing dose rate was limited to 0.75 Mrad/sec due to accelerator limitations.

Palma, G. E.↗
NASA NTRS1987

Thermal ion complexities observed within the Spacelab 2 bay

Examples of prominent thermal ion composition variations characteristic of the Shuttle environment as observed from within the open cargo bay on the Spacelab 2 mission are discussed. Although the prominent ionization source is the inflow of the ambient plasma, water ions of Shuttle origin were present throughout the mission, and there was evidence for a local source of molecular ions NO(+) and/or O(2+) which also exist in the ionosphere. Bursts in the fluxes of these contaminant species were frequently observed coincident with thruster firings, while O(+) depletions or enhancements could occur depending on the scattering geometry. These effects bring into question whether reliable ambient thermal ion measurements can be made from the vicinity of such vehicles. The presence of significant inflows of contaminant ions into the bay within the Shuttle wake also indicates that Shuttle emissions play a significant role in the evolution of its wake structure.

Grebowsky, J. M.↗
NASA NTRS2012

Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars

A front-end instrument, the laser ablation ion funnel, was developed, which would ionize rock and soil samples in the ambient Martian atmosphere, and efficiently transport the product ions into a mass spectrometer for in situ analysis. Laser ablation creates elemental ions from a solid with a high-power pulse within ambient Mars atmospheric conditions. Ions are captured and focused with an ion funnel into a mass spectrometer for analysis. The electrodynamic ion funnel consists of a series of axially concentric ring-shaped electrodes whose inside diameters (IDs) decrease over the length of the funnel. DC potentials are applied to each electrode, producing a smooth potential slope along the axial direction. Two radio-frequency (RF) AC potentials, equal in amplitude and 180 out of phase, are applied alternately to the ring electrodes. This creates an effective potential barrier along the inner surface of the electrode stack. Ions entering the funnel drift axially under the influence of the DC potential while being restricted radially by the effective potential barrier created by the applied RF. The net result is to effectively focus the ions as they traverse the length of the funnel.

Johnson, Paul V.↗
DOE OSTI2023

Tomographic optical emission spectroscopy of an atmospheric pressure plasma jet and surface ionization waves on planar and structured surfaces

Here in this paper, an approach for 3D plasma structure diagnostics using tomographic optical emission spectroscopy (Tomo-OES) of a nanosecond pulsed atmospheric pressure plasma jet (APPJ) is presented. In contrast to the well-known Abel inversion, Tomo-OES does not require cylindrical symmetry to recover 3D distributions of plasma light emission. Instead, many 2D angular projections are measured with intensified cameras and the multiplicative algebraic reconstruction technique is used to recover the 3D distribution of light emission. This approach solves the line-of-sight integration problem inherent to optical diagnostics, allowing recovery of localized OES information within the plasma that can be used to better infer plasma parameters within complex plasma structures. Here, Tomo-OES was applied to investigate an APPJ operated with helium in ambient air and impinging on planar and structured dielectric surfaces. Surface charging caused the guided streamer from the APPJ to transition to a surface ionization wave (SIW) that propagated along the surface. The SIW experienced variable geometrical and electrical material properties as it propagated, leading to 3D configurations that were non-symmetric and spatially complex. Light emission from He, N$_2^+$, and N2 were imaged at ten angular projections and the respective time-resolved 3D emission distributions in the plasma were then reconstructed. The spatial resolution of each tomographic reconstruction was 7.4 µm and the temporal resolution was 5 ns, sufficient to observe the guided streamer and the effects of the structured surface on the SIW. Emission from He showed the core of the jet and emission from N$_2^+$ and N2 indicated effects of entrainment of ambient air. Penning ionization of N2 created a ring or outer layer of N$_2^+$ that spatially converged to form the 'plasma bullet' or spatially diverged across a surface as part of a SIW. The SIW entered trenches of size 150 µm, leading to decreases in plasma light emission in regions above the trenches. The plasma light emission was higher in some regions with trenches, possibly due to effects of field enhancement.

plasma interactions with complex surfaces↗
NASA NTRS1988

High-resolution emission-line imaging of Seyfert galaxies. I - Observations. II - Evidence for anisotropic ionizing radiation

A CCD direct imaging survey of 11 Seyfert galaxies with a mean seeing of 1.3 arcsec FWHM is presented. It is found that the major axes and spatial scales of the circumnuclear emission-line gas are very similar to those of the radio continuum sources. In the second part, this close connection between thermal and relativistic gases is examined. A scenario is proposed in which the radio jets and plasmoids shock, accelerate, and compress ambient and entrained gas, with the dominant source of ionization being the nonstellar nuclear UV continuum.

Haniff, Christopher A.↗
DOE OSTI2020

Matrix-Assisted Ionization of Molecular Uranium Species

Matrix-assisted ionization (MAI) demonstrates high sensitivity for a variety of organic compounds; however, few studies have reported the application of MAI for the detection and characterization of inorganic analytes. Trace-level uranium analysis is important in the realms of nuclear forensics, nuclear safeguards, and environmental monitoring. Traditional mass spectrometry methods employed in these fields require combinations of extensive laboratory chemistry sample preparation and destructive ionization methods. There has been recent interest in exploring ambient mass spectrometry methods that enable timely sample analysis and higher sensitivity than what is attainable by field-portable radiation detectors. Rapid characterization of uranium at nanogram levels is demonstrated in this study using MAI techniques. Mass spectra were collected on an atmospheric pressure mass spectrometer for solutions of uranyl nitrate, uranyl chloride, uranyl acetate, and uranyl oxalate utilizing 3-nibrobenzonitrile as the ionization matrix. The uranyl complexes investigated were detectable, and the chemical speciation was preserved. Sample analysis was accomplished in a matter of seconds, and limits of detection of 5 ng of uranyl nitrate, 10 ng of uranyl oxalate, 100 ng of uranyl chloride, and 200 ng of uranyl acetate were achieved. The observed gas-phase speciation was similar to negative-ion electrospray ionization of uranyl compounds with notable differences. Six matrix-derived ions were detected in all negative-ion mass spectra, and some of these ions formed adducts with the uranyl analyte. Subsequent analysis of the matrix suggests that these molecules are not matrix contaminants and are instead created during the ionization process.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
NASA NTRS1983

Low-temperature Positron Annihilation

For a satisfactory understanding of astrophysical annihilation radiation, especially that observed from the galactic center direction, the interaction of positrons with the ambient medium must be carefully investigated. Although hot, ionized regions may be important sources of annihilation radiation, the simpler processes occurring in low-temperature neutral hydrogen gas are mainly addressed. The goal is to set limits on conditions in the annihilation region by using the predictions of atomic theory compared with the observed gamma-ray line width, continuum strength and time dependence.

Drachman, R. J.↗
NASA NTRS1983

Low-temperature positron annihilation

For a satisfactory understanding of astrophysical annihilation radiation, especially that observed from the Galactic center direction, the interaction of positrons with the ambient medium must be carefully investigated. Although hot, ionized regions may be important sources of annihilation radiation, the simpler processes occurring in low-temperature neutral hydrogen gas are mainly addressed. The goal is to set limits on conditions in the annihilation region by using the predictions of atomic theory compared with the observed gamma-ray line width, continuum strength and time dependence.

Drachman, R. J.↗