SEARCH · Search NASA

Results for “EV Charging”

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.

SourceResearch connectionFrom yearThrough year

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

At least 163 records · Page 9

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Deep diode arrays for X-ray detection

Temperature gradient zone melting process was used to form p-n junctions in bulk of high purity silicon wafers. These diodes were patterned to form arrays for X-ray spectrometers. The whole fabrication processes for these X-ray detectors are reviewed in detail. The p-n junctions were evaluated by (1) the dark diode I-V measurements, (2) the diode C sub I - V measurements, and (3) the MOS C-V measurements. The results showed that these junctions were linearly graded in charge distribution with low reverse bias leakage current flowing through them (few nA at -10 volts). The X-ray detection experiments showed that an FWHM of 500 eV was obtained from these diodes with a small bias of just -5 volts (for X-ray source Fe55). A theoretical model was proposed to explain the extra peaks found in the energy spectra and a very interesting point - cross talk effect was pointed out. This might be a solution to the problem of making really high resolution X-ray spectrometers.

Zemel, J. N.↗

NASA NTRS1984

Spectral characteristics of two types of low latitude aurorae

Attention is given to two types of aurorae whose low altitude emissions seem to be due to energy loss from trapped ring current ions or electrons whose energy is of the order of 1 eV. The spectral characteristics which predominate in the first type of aurora indicate direct precipitation of ring current particles as ions, and/or indirect precipitation as energetic neutrals, following charge transfer with exospheric H or O neutrals. The spectral characteristics of the second type indicate excitation by electrons and can yield brighter displays. The time variations of the emissions are found to be closely related to fluctuations of periods shorter than an hour in the magnetograms from nearby observatories.

Tinsley, B. A.↗

NASA NTRS1972

Ion heating mechanism in a modified Penning discharge

Ions with Maxwellian energy distributions and kinetic temperatures ranging from 20 eV to 7 keV have been observed in a modified Penning discharge operating in the steady state. Investigation of the plasma revealed two distinct spoke-like concentrations of charge rotating with different velocities in the sheath between the plasma and the anode ring. The faster spoke consists of electrons rotating with the E/B drift velocity, where E is the electric field and B is the magnetic field strength. The slow spoke consists of ions, the thermal velocity of which is observed to be proportional to the spoke velocity. The experimental data are consistent with a model whereby the ion drift velocity in this spoke, corresponding to kilovolt ion energies, is Maxwellianized by strong electrostatic turbulence in the sheath. Theoretical expressions are derived for the frequency of the electron and ion spoke rotation, for the ion kinetic temperature, and for the ion heating efficiency as functions of the discharge parameters. These expressions are shown to be consistent with extensive experimental data.

Roth, J. R.↗

NASA NTRS1972

Direct observation of the lunar photoelectron layer.

The Charged-Particle Lunar Environment Experiment (CPLEE), a part of the Apollo 14 ALSEP, is an ion-electron spectrometer capable of measuring ions and electrons with energies between 40 eV and 50 keV. Accordingly, the instrument, with apertures 26 cm above the surface, has detected a layer of photoelectrons, or photoelectron gas above the sunlit lunar surface with energies ranging up to 200 eV. The experimental data for periods when the moon was in the earth's magnetotail for electron energies between 40 and 200 eV follows a defined power-law spectrum. The implications of this measurement are two-fold in that the lunar surface potential can be immediately determined to be at least 200 V, and a value of the photoelectron yield of the lunar surface material for photon energies above 40 eV may be computed.

Reasoner, D. L.↗

NASA NTRS1979

Physical processes in directed ion beam sputtering

The general operation of a discharge chamber for the production of ions is described. A model is presented for the magnetic containment of both primary and secondary or Maxwellian electrons in the discharge plasma. Cross sections were calculated for energy and momentum transfer in binary collisions between like pairs of Ar, Kr, and Xe atoms in the energy range from about 1 eV to 1000 eV. These calculations were made from available pair interaction potentials using a classical model. Experimental data from the literature were fit to a theoretical expression for the Ar resonance charge exchange cross section over the same energy range. A model was developed that describes the processes of conical texturing of a surface due to simultaneous directed ion beam etching and sputter deposition of an impurity material. This model accurately predicts both a minimum temperature for texturing to take place and the variation of cone density with temperature. It also provides the correct order of magnitude of cone separation. It was predicted from the model, and subsequently verified experimentally, that a high sputter yield material could serve as a seed for coning of a lower sputter yield substrate. Seeding geometries and seed deposition rates were studied to obtain an important input to the theoretical texturing model.

Robinson, R. S.↗

NASA NTRS1986

The AXAF CCD imaging spectrometer

The AXAF CCD Imaging Spectrometer (ACIS) is currently being defined as a possible focal plane instrument to be flown on the Advanced X-ray Astrophysics Facility (AXAF). The imaging spectrometer consists of an array of charge coupled devices (CCD's) to be placed at the focus of the AXAF mirrors. The array will provide high angular resolution (0.5 arc seconds), moderate spectral resolution (150 eV) over the energy range 0.1 to 10 keV, temporal resolution down to 60 microseconds, and single photon quantum detection efficiencies of up to 90 percent. X-ray sensitivity for a point source exceeds 10 to the -15th ergs/sq cm sec for a 10 to the 5th sec exposure. When used in conjunction with the objective gratings, the array will yield wavelength resolution of up to 200.

Garmire, G. P.↗

NASA NTRS1986

Carrier surface generation and recombination effects in photoconduction of HgI2 single crystals

Dc photoconductivity characteristics of HgI2 single crystals have been measured in the range of 1.75-2.75 eV, using CuI as a transparent electrical contact. Hole and electron photocurrents could be separately measured by applying different voltage polarities to the illuminated electrode. It is shown that charge carrier generation near the surface is highly extrinsic, as displayed by differences in the hole and electron photogeneration spectra. Analysis of the photoconductivity versus voltage characteristics indicates that the hole and electron bulk trapping times satisfy greater than 70 and 3 microsec, respectively. The hole and electron surface recombination velocities were 1.0 x 10 to the 4th cm/s and 8 x 10 to the 5th cm/s, respectively.

Burshtein, Z.↗

NASA NTRS1988

Hydrogen line and continuum emission in young stellar objects. I - Excitation model

Two mechanisms that populate the n = 2 level of hydrogen after the Lyman continuum is depleted are identified. They are ionization of N I from its excited states, followed by charge-exchange between N II and H I, and Ly-beta line wing absorption. Both processes involve absorption of the sub-Lyman continuum between 11 and 13.6 eV. With population in level n = 2 thus maintained, the strong Brackett line fluxes observed are then produced as a result of Balmer photoionization. The magnitude of the sub-Lyman continuum dictates the fraction of Balmer continuum that will be absorbed. Numerical calculations for four young stellar objects with luminosity ranging from 10 to 10,000 solar are performed, and it is concluded that this two-step process of sub-Lyman continuum absorption followed by Balmer photoionization can account for the great majority of observed Brackett line fluxes. The location and mass of the emitting as as determined from the Brackett line fluxes are reported. The Br-alpha luminosity is calculated as a function of the mass loss rate.

Kwan, John↗

NASA NTRS1991

A resistive-gate In(0.53)Ga(0.47)As/InP heterostructure CCD

The first InGaAs/InP charge-coupled device is demonstrated, exhibiting a charge transfer efficiency (CTE) of 0.98 at 13 MHz and 1 GHz. Cooling the device improves the CTE to greater than 0.99 at 13-MHz clock frequency. The 0.76-eV In(0.53)Ga(0.47)As bandgap makes this structure applicable to direct-detection short-wavelength infrared imagers.

Rossi, D. V.↗

NASA NTRS1993

Pulsed, gridded electron reversal ionizer

The design and performance of a new-type source of negative ions is presented. This device retains the idea of the so-called reversal electron attachment detector to produce low-energy electrons by reversing electron trajectories at an electrode. Electrons are produced in the present device by several ribbon filaments that surround a cylindrical wire grid. They are accelerated through the grid, then decelerated to zero or near-zero velocity at the surface of a tube. The tube (anode) is perforated with small holes through which effuse the target molecules. Electrons attach to form either parent and/or fragment negative ions. Attachment takes place at a location above the anode corresponding to a match between the electron energy and the attachment resonance energy. Negative ions are pulsed out of the attachment region and focused onto the entrance plane of a quadrupole mass selector. Electron and ion trajectory calculations are presented and the performance illustrated with six molecules having attachment resonances in the range 0.0-2.2 eV. The detection sensitivity is below 1 part-per-trillion, with a calculated conversion rate of 1.3 percent. Signal nonlinearity is discussed in terms of ion space-charge effects. The device also produces positive ions, and an analogous treatment may be carried through to characterize its performance in this mode.

Boumsellek, S.↗

NASA NTRS2010

Turbomolecular Pumps for Holding Gases in Open Containers

Proposed special-purpose turbomolecular pumps denoted turbotraps would be designed, along with mating open containers, to prevent the escape of relatively slowly (thermal) moving gas molecules from the containers while allowing atoms moving at much greater speeds to pass through. In the original intended applications, the containers would be electron-attachment cells, and the contained gases would be vapors of alkali metal atoms moving at thermal speeds that would be of the order of a fraction of 300 meters per second. These cells would be parts of apparatuses used to measure fluxes of neutral atoms incident at kinetic energies in the approximate range of 10 eV to 10 keV (corresponding to typical speeds of the order of 40,000 m/s and higher). The incident energetic neutral atoms would pass through the cells, wherein charge-exchange reactions with the alkali metal atoms would convert the neutral atoms to negative ions, which, in turn, could then be analyzed by use of conventional charged-particle optics.

Keller, John W.↗

NASA NTRS1972

Characteristics of the lunar photoelectron layer in the geomagnetic tail.

The charged particle lunar environment experiment, a part of the Apollo 14 lunar surface package, is an ion-electron spectrometer capable of measuring ions and electrons with energies between 40 eV and 50 keV. The instrument, with apertures 26 cm above the surface, has detected a photoelectron gas layer above the sunlit lunar surface. No detectable flux above 200 eV has been observed. Experimental data for periods while the moon was in the earth's magnetotail for electrons with energies 40 eV less than or equal to 200 eV follow a power-law spectrum. In the absence of photoelectrons with E greater than 200, we assume that the surface potential is at least 200 V. The modulation of this potential in the presence of intense plasma-sheet fluxes has been observed. Also, a detailed history of the Feb. 10, 1971, total lunar eclipse, to determine the source distribution of high-energy solar photons, is presented.

Reasoner, D. L.↗

NASA NTRS1978

The significance of gamma ray observations for neutrino astronomy

Celestial gamma-rays and neutrinos are formed in some of the same astrophysical interactions, but have important different properties. Measurements of these radiations were used to study the presence and dynamic effects of energetic charged cosmic ray particles, element synthesis and particle acceleration. In addition, since gamma-rays in the energy range from several MeV to at least 10 to the 12th power eV and neutrinos both have very low interaction cross sections, they have a very high penetrating power and reach the earth from almost any part of the galaxy or universe. Therefore, they retain the detailed imprint of spectral, directional and temporal features imposed at their birth, even if they were born in regions opaque to visible light and X-rays.

Fichtel, C. E.↗

NASA NTRS1996

Electron Flow to a Satellite at High Positive Potential

The Tethered Satellite System (TSS) is designed to deploy a 1.6 m diameter spherical satellite a distance of 20 km above the space shuttle orbiter on an insulated conducting tether. Because of the passage of the conducting tether through the earth's magnetic field, an emf is generated producing a positive satellite potential of about 5000 V. Electron flow under the influence of this high positive potential is the focus of the present analysis. The ionospheric parameters at TSS orbit altitude are; thermal velocity of electrons, 1.9 x 10(exp 5) M/S, thermal velocity of the ions, 1.1 x 10(exp 3) m/s, velocity of the satellite 8 x 10(exp 3) m/s. The electrons, with a Debye length, lambda(D) = 0.49 cm, spiral about the earth's magnetic field lines (0.4 Gauss) with a radius of about 3 cm and the ions spiral with a radius of 5 m. Under these conditions, the electron thermal energy, kT is 0.17 eV. The TSS satellite radius, r(p) is 163 Debye lengths. There is an extensive literature on the interaction of satellites with the near-earth ionospheric plasma. The space charge limitation to the electron current collected by a sphere at positive electrical potential was calculated by Langmuir and Blodgett (1924). Parker and Murphy (1967) recognized the importance of the influence of the earth's magnetic field and used the guiding center approximation to calculate the electron current collected by a positive charged satellite. More recently Ma and Schunk (1989) have calculated the time dependent flow of electrons to a spherical satellite at positive potential utilizing numerical methods and Sheldon (1994) used similar methods to solve this problem for the steady state. In order to analyze some of the phenomena that occurred in the ionosphere during the TSS flights, it would be useful to have analytic expressions for these electron flows. The governing equations are very complex and an exact analytical solution is not likely. An approximate analytical solution is feasible however, and the results of one attempt are presented herein.

Sheldon, John W.↗

NASA NTRSDate not supplied

L2-Charged Particle Environment (L2-CPE)Low Energy Radiation Fluence Model

The L2 Charged Particle Environment (L2-CPE) model provides estimates of number flux and fluence for the low energy electron, proton, and alpha particle populations in the near Earth solar wind and the Earth’s distant magnetosheath and magnetotail. The model is an engineering tool for specifying radiation environments over an energy range from a few eV to a few MeV of importance to surface dose and radiation damage to thin space exposed materials and is intended for use in space system design applications. Mission fluences are obtained by simulating a spacecraft flight trajectory through time-dependent bow shock and magnetopause boundaries with dimensions and orientations driven by solar wind parameters. Monte Carlo sampling of flux environments within individual plasma regimes and/or fluence accumulated along a fight trajectory through multiple regimes is used to determine statistical variations (means and extremes) of the differential number flux and fluence environments for each of the three charged particle species. Model output is differential (in energy) number fluence and flux for the three particle species in units of particles/cm2-keV and particles/cm2-sec-keV, respectively. Users can select the energy range of interest but the current version of the code (L2-CPE Version 1.4.2d) is limited to an energy range of 1 eV to 10 MeV. Flux is integrated over angle to give flux and fluence to surfaces in the ±XGSE, ±YGSE, and/or ±ZGSE directions. Figure 1 shows the opening screen from the L2-CPE graphical user interface (GUI) with options for flux, fluence, plotting model output. The flux scene generate is not currently implemented in the GUI.

Joseph I Minow↗

NASA NTRS2020

Quantifying the Effect of Cosmic Ray Showers on the X-IFU Energy Resolution

The X-ray Integral Field Unit (X-IFU) will operate an array of more than 3000 Transition Edge Sensor pixels at 90 mK with an unprecedented energy resolution of 2.5 eV at 7 keV. In space, primary cosmic rays and secondary particles produced in the instrument structure will continuously deposit energy on the detector wafer and induce fluctuations on the pixels’ thermal bath. We have investigated through simulations of the X-IFU readout chain how these fluctuations eventually influence the energy measurement of X-ray photons. Realistic timelines of thermal bath fluctuations at different positions in the array are generated as a function of a thermal model and the expected distribution of the deposited energy of the charged particles. These are then used to model the TES response to these thermal perturbations and their influence on the onboard energy reconstruction process. Overall, we show that with adequate heatsinking, the main energy resolution degradation effect remains minimal and within the associated resolution allocation of 0.2 eV. We further study how a dedicated triggering algorithm could be put in place to flag the rarer large thermal events.

P. Peille↗

NASA NTRS1984

Results from the Helios galactic and solar cosmic ray experiment (E7)

Energy spectra, charge composition, and flow patterns of solar and galactic cosmic rays were investigated using three nuclear-particle telescopes on Helios to measure electrons (50 keV to 8 MeV) protons (100 eV to 800 MeV) alpha particles (to 600 MeV per nucleon) heavier elements up to neon, (to 200 MeV per nucleon). The experiment includes a proportional counter to monitor solar X-rays in the range 2 to 8 keV. A collection of solar flare associated particle events are observed whereby coronal effects and spatial distribution of flare particles are determined over almost a whole solar cycle; a typical solar particle events are also observed. Earlier explanations concerning corotating energetic particle streams in the inner and outer solar system are confirmed. Solar modulation of galactic cosmic rays is identified. Gamma ray bursts are detected and the sources in the sky are precisely determined, proving the suspected galactic origin.

Trainor, J. H.↗

NASA NTRS1992

Giotto data analysis: Electron plasma and heavy ion composition measurements at Comet Halley

This investigation involved the analysis of electron plasma and heavy ion composition measurements made by the COPERNIC (COmplete Positive ion, Electron, and Ram Negative Ion measurements near Comet Halley) plasma experiment during the close fly-by of Halley by the European Space Agency's Giotto spacecraft. The experiment provided measurements of the full 3-dimensional distribution of 10 eV-30 keV electrons, and mass analysis of cold cometary ions from 10-210 amu. The analysis of the COPERNIC data has yielded some remarkable results, including: The discovery of negatively charged ions in the inner coma; the discovery of far heavier (mass is greater than 50 amu) ions than predicted, dominated by complex molecular ions made up of C, H, O, and N; the discovery of an adiabatic heating effect on electrons from the compression of the solar wind plasma; the identification of several organic and sulfur bearing ions; and the discovery of a new 'mystery region' where electrons are accelerated to high energies. These discoveries were in addition to the detailed analysis of 'expected' features at Comet Halley. Although this grant has expired, analysis continues on the data at a low (unfunded) level, and it is expected that more significant results will be obtained. A bibliography of the papers resulting from this research is attached, and a copy of each paper is included.

Lin, Robert P.↗