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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Design, development, and fabrication of a electronic analog microminiaturized electronic analog signal to discrete time interval converter

The microminiaturization of an electronic analog signal to discrete time interval converter is presented. Discrete components and integrated circuits comprising the converter were assembled on a thin-film ceramic substrate containing nichrome resistors with gold interconnections. The finished assembly is enclosed in a flat package measuring 3.30 by 4.57 centimeters. The module can be used whenever conversion of analog to digital signals is required, in particular for the purpose of regulation by means of pulse modulation. In conjunction with a precision voltage reference, the module was applied to control the duty cycle of a switching regulator within a temperature range of -55 C to +125 C, and an input voltage range of 10V to 35V. The output-voltage variation was less than + or - 300 parts per million, i.e., less than + or - 3mV for a 10V output.

Schoenfeld, A. D.↗
NASA NTRS1973

Electron impact excitation and assignment of the low-lying electronic states of N2O

Electron scattering spectra of nitrous oxide are reported in the 5- to 10-eV energy-loss range at scattering angles of 20, 30, 90, and 130 deg at a residual energy of 7.0 eV; and at residual energies of 10.0, 2.0, 1.0, 0.6, and 0.2 eV at a scattering angle of 90 deg. Several new distinct and overlapping continua are observed to lie in this energy-loss range. The experimental spectra are discussed in the light of semiempirical INDO calculations of Chutjian and Segal (1972) of the vertical transition energies of N2O. An assignment of the symmetries of the observed excitations consistent with the experimental and theoretical data is suggested.

Hall, R. I.↗
NASA NTRS1977

The plasma line revisited as an aeronomical diagnostic - Suprathermal electrons, solar EUV, electron-gas thermal balance

Spectra of plasma wave intensities in the ionosphere over Arecibo are calculated and compared with those from observations of the plasma line intensity. This approach involving directly observed quantities avoids the uncertainties that have plagued past comparisons with photoelectron theory. In addition, careful comparisons in physically relevant segments of the spectra show that any significant increase in the magnitude of the solar EUV flux would lead to a contradiction of the observed plasma wave intensities. Further, the comparisons indicate that resolution of the thermal electron-gas heat balance problem must be sought through better heat transfer rates (e.g., heating and cooling rates, etc.), rather than in the solar EUV. This approach utilizes more fully the potential of the plasma line experiment as a diagnostic tool for aeronomical studies, (e.g., photoelectrons, auroral secondaries, ionosphere-modification experiments, etc.).

Carlson, H. C., Jr.↗
NASA NTRS1980

Electron-temperature dependence of dissociative recombination of electrons with CO(+)-(CO)n-series ions

A microwave afterglow mass spectrometer apparatus is used to determine the dependence on electron temperature T sub e of the recombination coefficients alpha sub n of the dimer and trimer ions of the series CO+.(CO) sub n. It is found that alpha sub 1 = (1.3 + or - 0.3)x 0.000001 (T sub e(K)/300) to the -0.34; and alpha sub 2 = (1.9 + or - 0.4)x 0.000001 (T sub e(K)/300) to the -0.33 cu cm/sec. These dependences on T sub e are quite different from those obtained previously for polar-cluster ions of the hydronium and ammonium series but are similar to that for simple diatomic ions.

Whitaker, M.↗
NASA NTRS1980

The energy loss of relativistic electrons in energetic photon gases and its relation to the equilibrium spectrum of electrons

The energy loss of relativistic electrons is considered for astrophysical objects which contain energetic photon gases in the XUV-range. Such objects have been suggested as possible candidates for gamma-ray point sources through the mechanism of inverse Compton scattering. In certain cases where inverse Compton scattering is the dominant energy loss mechanism, an equilibrium spectrum results which can deviate from a strict power law. Such an effect can have consequences on the observed radiation spectrum from such objects.

Prince, T.↗
NASA NTRS1982

Free-electron laser from wave-mechanical beats of 2 electron beams

It is possible, though technically difficult, to produce beams of free electrons that exhibit beats of a quantum mechanical nature. (1) the generation of electromagnetic radiation, e.g., light, based on the fact that the beats give rise to alternating charge and current densities; and a frequency shifter, based on the fact that a beam with beats constitutes a moving grating. When such a grating is exposed to external radiation of suitable frequency and direction, the reflected rediation will be shifted in frequency, since the grating is moving. A twofold increase of the frequency is readily attainable. It is shown that it is impossible to generate radiation, because the alternating electromagnetic fields that accompany the beats cannot reform themselves into freely propagating waves. The frequency shifter is useless as a practical device, because its reflectance is extremely low for realizable beams.

Lichtenstein, R. M.↗
NASA NTRS1984

Electron-beam induced current characterization of back-surface field solar cells using a chopped scanning electron microscope beam

A chopped electron beam induced current (EBIC) technique for the chacterization of back-surface field (BSF) solar cells is presented. It is shown that the effective recombination velocity of the low-high junction forming the back-surface field of BSF cells, in addition to the diffusion length and the surface recombination velocity of the surface perpendicular to both the p-n and low-high junctions, can be determined from the data provided by a single EBIC scan. The method for doing so is described and illustrated. Certain experimental considerations taken to enhance the quality of the EBIC data are also discussed.

Luke, K. L.↗
NASA NTRS1985

Integral functions of electron lateral distribution and their fluctuations in electron-photon cascades

Monte Carlo simulated lateral distribution functions for electrons of EPC developing in lead, at superhigh energies (.1-1 PeV) for depths t or = 60 c.u. delta t=1t. c.u. are presented. The higher moment characteristics, i.e., variation, asymmetry, excess, are presented along with analytical solutions for the same characteristics at fixed observation level calculated to theory approximations A and B by using numerical inversion of the Laplace transformation. The conclusion is made of a complex, usually non-Gaussian shape of the function of the particle number distribution within a circle of given radius at fixed depth.

Ivanenko, I. P.↗
NASA NTRS1984

Electron-atom spin asymmetry and two-electron photodetachment - Addenda to the Coulomb-dipole threshold law

Temkin (1982) has derived the ionization threshold law based on a Coulomb-dipole theory of the ionization process. The present investigation is concerned with a reexamination of several aspects of the Coulomb-dipole threshold law. Attention is given to the energy scale of the logarithmic denominator, the spin-asymmetry parameter, and an estimate of alpha and the energy range of validity of the threshold law, taking into account the result of the two-electron photodetachment experiment conducted by Donahue et al. (1984).

Temkin, A.↗
NASA NTRS1987

Structural characterization and gas reactions of small metal particles by high resolution in-situ TEM (Transmission Electron Microscopy) and TED (Transmission Electron Diffraction)

The detection and size analysis of small metal particles supported on amorphous substrates becomes increasingly difficult when the particle size approaches that of the phase contrast background structures of the support. An approach of digital image analysis, involving Fourier transformation of the original image, filtering, and image reconstruction was studied with respect to the likelihood of unambiguously detecting particles of less than 1 nm diameter on amorphous substrates from a single electron micrograph.

Heinemann, K.↗
NASA NTRS1987

Electron attachment in F2 - Conclusive demonstration of nonresonant, s-wave coupling in the limit of zero electron energy

Dissociative electron attachment to F2 has been observed in the energy range 0-140 meV, at a resolution of 6 meV (full width at half maximum). Results show conclusively a sharp, resolution-limited threshold behavior consistent with an s-wave cross section varying as sq rt of epsilon. Two accurate theoretical calculations predict only p-wave behavior varying as the sq rt of epsilon. Several nonadiabatic coupling effects leading to s-wave behavior are outlined.

Chutjian, A.↗
NASA NTRS1988

Characterization of electron-beam induced damage structures in natural fluorite, CaF2, by analytical electron microscopy

This paper describes the damage structure induced in natural CaF2 by the electron beam when using TEM. The observed 10-20 nm periodic features with coherent fringe patterns and the pronounced loss of fluorine found after the TEM exposure of 100-line-oriented and 111-oriented sections of CaF2 provides support for the mechanism of damage by decomposition of CaF2 into 2F and Ca, with the Ca precipitates maintaining a close topotaxial relationship with the parent CaF2.

Blake, D. F.↗
NASA NTRS1991

Absolute differential cross sections for electron capture and loss by kilo-electron-volt hydrogen atoms

This paper reports measurements of absolute differential cross sections for electron capture and loss for fast hydrogen atoms incident on H2, N2, O2, Ar, and He. Cross sections have been determined in the 2.0- to 5.0-keV energy range over the laboratory angular range 0.02-2 deg, with an angular, resolution of 0.02 deg. The high angular resolution allows observation of the structure at small angles in some of the cross sections. Comparison of the present results with those of other authors generally shows very good agreement.

Smith, G. J.↗
NASA NTRS1992

Electron attachment to molecules at ultralow electron energies

Experimental techniques, both single-collision and multiple-collision, for studying electron attachment to molecules at energies below 0.1 eV are reviewed. Recent attachment results in HI, DI, F2, SF6, CCl4, and CFCl3 are examined from the point of view of threshold behavior (s- or p-wave), threshold energetics, and the temperature dependence of the attachment rate constant. An interesting application of the s-wave phenomenon to trace-species detection is given.

Chutjian, Ara↗
NASA NTRS1995

NASA wide electronic publishing system: Electronic printing and duplicating. Stage 3 evaluation report

The report is presented in four sections: The Introduction describes the duplicating configuration under evaluation and the Background contains a chronological description of the evaluation segmented by phases 1 and 2. This section includes the evaluation schedule, printing and duplicating requirements, storage and communication requirements, electronic publishing system configuration, existing processes and proposed processes, billing rates, costs and productivity analysis, and the return on investment based upon the data gathered to date. The third section contains the phase 1 comparative cost and productivity analysis. This analysis demonstrated that LaRC should proceed with a 90-day evaluation of the DocuTech and follow with a phase 2 cycle to actually demonstrate that the proposed system would meet the needs of LaRC's printing and duplicating requirements, benchmark results, cost comparisons, benchmark observations, and recommendations. These are documented after the recommendations.

Tuey, Richard C.↗
NASA NTRS2004

Determination of the Three-Dimensional Morphology of ALH84001 and Biogenic MV-1 Magnetite: Comparison of Results from Electron Tomography and Classical Transmission Electron Microscopy

Dated at approximately 3.9 billion years of age, carbonate disks, found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature in an aqueous medium. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately one quarter of these magnetites have morphological and chemical similarities to magnetite particles produced by magnetotactic bacteria strain MV-1, which are ubiquitous in aquatic habitats on Earth. Moreover, these types of magnetite particles are not known or expected to be produced by abiotic means either through geological processes or synthetically in the laboratory. The remaining three quarters of the ALH84001 magnetites are likely products of multiple processes including, but not limited to, precipitation from a hydrothermal fluid, thermal decomposition of the carbonate matrix in which they are embedded, and extracellular formation by dissimilatory Fe-reducing bacteria. We have proposed that the origins of magnetites in ALH84001 can be best explained as the products of multiple processes, one of which is biological. Recently the three-dimensional (3-D) external morphology of the purported biogenic fraction of the ALH84001 magnetites has been the subject of considerable debate. We report here the 3-D geometry of biogenic magnetite crystals extracted from MV-1 and of those extracted from ALH84001 carbonate disks using a combination of high resolution classical and tomographic transmission electron microscopy (TEM). We focus on answering the following questions: (1) which technique provides adequate information to deduce the 3-D external crystal morphology?; and, (2) what is the precise 3-D geometry of the ALH84001 and MV-1 magnetites?

Thomas-Keprta, Kathie L.↗
NASA NTRS2005

The Space Radiation Environment as it Relates to Electronic System Performance: Or Why Not to Fly Commercial Electronic Components in Space

This viewgraph presentation offers an overview of the space radiation environment, primarily in near-Earth environments such as Low Earth Orbit (LEO). The presentation describes the Halloween solar event of 2003 as an example of how solar activity can affect spacecraft electronic systems. The lunar radiation environment is also briefly summarized.

Barth, Janet L.↗