Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ENERGY DEPENDENCE”

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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Interplanetary acceleration of relativistic electrons observed with IMP 7

The intensities of 0.22- to 0.5-MeV and 0.5- to 0.8-MeV electrons in interplanetary space following the Oct. 29, 1972, solar particle event have been observed by the IMP 7 satellite. Intensity variations associated with the SSC disturbance of 1655 UT on October 31 are interpreted as suggesting interplanetary acceleration. The results are consistent with an energy-dependent acceleration process which is most effective for electrons of about 0.4 MeV. This is the first reported interplanetary-shock-wave acceleration of relativistic electrons of which the authors are aware.

Armstrong, T. P.↗
NASA NTRS1976

Molecular effect on equilibrium charge-state distributions

The paper describes an experiment consisting of the acceleration of N(+) and N2(+) ions to energies between 0.25 and 1.75 MeV and their injection through a thin carbon foil, whereupon they were charge-state analyzed with an electrostatic analyzer. A foil-covered electrically suppressed Faraday cup, connected to a stepping motor, moved in the plane of the dispersed beams. The Faraday cup current, which was proportional to the number of incident ions, was sent to a current digitizer and computer programmed as a multiscaler. The energy-dependent charge-state fractions, the mean charge and the distribution width were calculated. It was shown that for incident atoms, the charge state distribution appeared to be spread over more charge states, while for the incident molecules, there was a greater fraction of charge states near the mean charge.

Wickholm, D.↗
NASA NTRS1976

Spectral variability in the X-ray pulsar GX 1 + 4

Observations of the galactic-center-region hard X-ray source GX 1 + 4 by the GSFC X-ray spectroscopy experiment on OSO-8 confirm that GX 1 + 4 is a slow X-ray pulsar. The amount of absorption by cold matter in the spectrum of GX 1 + 4 varies significantly within a 24-hour period, which is typical of many X-ray binary systems. The light curve for the pulsations from GX 1 + 4 appears to be energy-dependent.

Becker, R. H.↗
NASA NTRS1976

Minima in generalized oscillator strengths for initially excited hydrogen-like atoms

Generalized oscillator strengths for transitions from an initially excited state of a hydrogenic atom to final states (either discrete or continuum) have complicated structures, including minima and shoulders, as functions of the momentum transfer. Extensive calculations carried out in the present work have revealed certain systematics of these structures. Some implications of the minima to the energy dependence of the inner-shell ionization cross section of heavy atoms by proton impact are discussed.

Matsuzawa, M.↗
NASA NTRS1975

Aluminum under high pressure. I - Equation of state

A curve of applied pressure versus lattice constant is calculated for single-crystal aluminum. It results from an application of the method of structural expansions for deriving the energies of simple metals, a method known to give reasonable results for the elastic constants even at second order in the effective electron-ion interaction. The latter is taken from Fermi-surface analysis, and it is verified that the extant face-centered cubic structure remains the preferred crystalline phase up to the highest pressures considered. Arguments are given to suggest that the curve should have reasonable a priori accuracy and can admit possible improvement if experimental data in the intermediate-pressure region can be provided to refine the (in principle) energy-dependent pseudopotential. At three megabars, the lattice constant is reduced by only 22 per cent; the ion cores at this pressure are still very well separated.

Friedli, C.↗
NASA NTRS1977

On the high energy proton spectrum measurements

The steepening of the proton spectrum beyond 1000 GeV and the rise in inelastic cross sections between 20 and 600 GeV observed by the PROTON-1-2-3 satellite experiments were explained by systematic effects of energy dependent albedo (backscatter) from the calorimeter.

Ellsworth, R. W.↗
NASA NTRS1978

The isotopic composition of cosmic-ray helium from 123 to 279 MeV per nucleon - A new measurement and analysis

A description is given of an experiment which was designed to measure the spectra and composition of cosmic-ray hydrogen and helium isotopes in the interval 120-280 MeV per nucleon to compare with the recent values observed at low energies and also with the only earlier measurement in this high-energy regime. The results presented were obtained during a high-altitude balloon flight from Thompson, Manitoba, in 1973 August. This flight occurred during the period in which the presence of the anomalous component in the helium spectrum became apparent, and provides the opportunity of determining whether this component extends to higher energies than those studied by satellite experiments. The results place an upper limit on the flux of 'anomalous' He-4 (which appeared at low energy in 1972) of at most 15% in the energy range of this experiment, and combined with the low-energy observations of the Chicago group, show an energy dependence of the average ratio of the helium isotopes in the modulated cosmic rays which is difficult to reconcile with current modulation models.

Leech, H. W.↗
NASA NTRS1979

Microplume model of spatial-yield spectra

An analytic representation for the spatial (radial and longitudinal) yield spectra is developed in terms of a model containing three simple 'microplumes'. The model is applied to electron energy degradation in molecular nitrogen gas for 0.1 to 5 keV incident electrons. From the nature of the cross section input to this model it is expected that the scaled spatial yield spectra for other gases will be quite similar. The model indicates that each excitation, ionization, etc. plume should have its individual spatial and energy dependence. Extensions and aeronomical and radiological applications of the model are discussed.

Green, A. E. S.↗
NASA NTRS1979

Elemental composition, isotopes, electrons and positrons in cosmic rays

Papers presented at the 16th International Cosmic Ray Conference, Kyoto, Japan, dealing with the composition of cosmic rays are reviewed. Particular interest is given to data having bearing on nucleosynthesis sites, supernovae, gamma-process, comparison with solar system composition, multiplicity of sources, and the energy dependence of composition.

Balasubrahmanyan, V. K.↗
NASA NTRS1979

HEAO-1 observations of AM Herculis between 0.1 and 3 keV

Results are reported for HEAO A2 scanning observations of AM Her in the energy range from 0.1 to 3 keV. A light curve of AM Her is plotted, a typical flux of 8 x 10 to the -10th erg/sq cm-sec in the 0.15-0.5-keV range at X-ray maximum is estimated, and no pronounced spectral variation with phase is detected. It is found that both a 0.025-keV blackbody spectrum and an exponential spectrum with an energy-dependent Gaunt factor provide an acceptable fit to the data. It is concluded that the spectrum of the radiation from the plasma at the surface of the strongly magnetic and relatively massive white dwarf in AM Her consists of three components: (1) a high-temperature (about 100 million to 1 billion K) component produced by electron-ion bremsstrahlung in the hot postshock plasma; (2) a blackbody component of about 100,000 to 1 million K produced by the heated surface of the white dwarf; and (3) a still softer component produced by optically thick electron cyclotron emission in the postshock region.

Tuohy, I. R.↗
NASA NTRS1979

Einstein Observatory /HEAO-B/ mirror design and performance

The mirrors for the Einstein Observatory represent a substantial advance in the state of the art X-ray optics, and have been tested more thoroughly than previous telescopes. The image is characterized by a narrow, wavelength independent core, and broad energy dependent wings. The width of the core is about that expected from mechanical and visible light measurements taken during fabrication and assembly. The wings of the response function are caused by microscopic surface scattering, but only a qualitative understanding of this process exists. Improvement in surface texture to reduce the wide angle scatter is the most urgent task in the development of large X-ray optics. The mirrors have survived the experiment integration period and launch, and are performing in orbit as they performed upon the ground.

Van Speybroeck, L. P.↗
NASA NTRS1980

The low energy plasma in the Jovian magnetosphere

Measurements below 6 keV from the plasma science experiment on the Voyager spacecraft show that positive ions with temperatures as low as 30 eV to several keV are observed to distances at least as great as 40 Jupiter radii in the dayside Jovian magnetosphere. When velocity determinations are possible between 10 and 40 Jupiter radii, the plasma velocity component along the rigid corotation direction is found to be consistently less than the full corotation speed. Positive ion measurements above 28 keV from the low energy charged particle experiment on Voyager demonstrate the existence of positive ions with temperatures of 20-30 keV at all distances greater than 30 Jupiter radii. Taken together, these observations suggest that the low energy plasma population from 30 to at least 40 Jupiter radii frequently contains both a cold and a hot component. A two-component plasma of this nature may indicate different sources, acceleration mechanisms, or time histories for the disparate components. It may also be indicative of a single acceleration mechanism which is highly energy dependent.

Belcher, J. W.↗
NASA NTRS1980

The effect of injection location on the spectrum of energetic magnetospheric particles

The role of local particle injections and accelerations in determining energetic particle spectra used as an indication of the radial diffusion of trapped magnetospheric particles is assessed. An idealized one-dimensional steady-state model of magnetospheric radial transport in which diffusion is balanced against particle sources and sinks is used to illustrate the effects of particle injection at a point and over a band of radii in which the observation point is immersed in particle spectra. For an injection spectrum uniformly distributed in space and a step function in energy, it is shown that the energy dependence of the measured spectrum is determined not only by adiabatic energization of the input spectrum but by the spatial structure of the injection and the radial dependence of the diffusion coefficient as well. The relevance of the results for observations of particle spectra in the terrestrial and Jovian magnetospheres is also considered

Birmingham, T. J.↗
NASA NTRS1980

Simultaneous X-ray and optical observations of rapid variability in Scorpius X-1

Copernicus and SAS-3 observations of Sco X-1 during very active states show strong and rapid X-ray flickering with time scales as short as 20 sec. Simultaneous optical photometry reveals similar and remarkably well correlated flickering of lower amplitude. The level of correlation decreases when the X-ray source becomes fainter, but optical and X-ray fluxes, averaged over 1 min, are usually well correlated for B magnitudes less than 12.9. Cross-correlation analysis of the data during periods of high activity shows no really significant time delay between X-ray and optical features, although the cross-correlation function peaks systematically for positive lag values (optical following X-rays). The amplitude of the X-ray flickering exhibits a strong energy-dependence consistent with the well-known intensity versus spectral-hardness relation derived from previous observations. The highly correlated optical activity is interpreted as due to reprocessing of X-ray photons in the binary system.

Ilovaisky, S. A.↗
NASA NTRS1980

Solar wind ion injections in the morning auroral oval

Energy versus time dispersion of precipitating ion bursts was observed during two rocket flights in the morning auroral oval. Individual bursts lasted about 20 seconds and repeated on a time scale of 100 seconds. The dispersion is interpreted as energy-dependent time-of-flight delay which provides identification of ion charge-to-mass ratio as well as injection source distance. The data are consistent with injections of magnetosheath ions with injection distances ranging from 7 to 19 earth radii. Individual events extended over a regin of at least several degrees of magnetic longitude and 0.3 degrees of invariant latitude. It is suggested that these events are associated with turbulent plasma entry into the magnetospheric entry layer.

Carlson, C. W.↗
NASA NTRS1981

Radiation studies of optical and electronic components used in astronomical satellite studies

The synchronous orbit of the IUE carries the satellite through Earth's outer electron belt. A 40 mCi Sr90 source was used to simulate these electrons. A 5 mCi source of Co60 was used to simulate bremmstrahlung. A 10 MeV electron Linac and a 1.7 MeV electron Van de Graaf wer used to investigate the energy dependence of radiation effects and to perform radiations at a high flux rate. A 100 MeV proton cyclotron was used to simulate cosmic rays. Results are presented for three instrument systems of the IUE and measurements for specific components are reported. The three instrument systems were the ultraviolet converter, the fine error sensor (FES), and the SEC vidicon camera tube. The components were optical glasses, electronic components, silicon photodiodes, and UV window materials.

Becher, J.↗
NASA NTRS1980

The elemental abundances of hydrogen through nickel in the low energy cosmic rays

The relative abundances of the elements H through Ni in the galactic cosmic rays have been measured in the energy range 70-280 MeV/nucleon with the University of Chicago cosmic ray telescope on board the satellite IMP-8 from January 1973 to September 1978. Cosmic ray source abundances have been derived by extrapolating the measured composition back to the source. A key factor in the propagation calculation is the use of a pathlength distribution and a solar modulation level shown to be consistent with the secondary to primary ratios and their energy dependence below about 1 GeV/n.

Garcia-Munoz, M.↗
NASA NTRS1980

The energy spectrum of cosmic ray electrons, 5-150 MeV in late 1978 and early 1979

The University of Chicago cosmic ray electron detector was launched aboard the ISEE-3 spacecraft on August 12, 1978. The energy spectrum of electrons measured in 1978 is nearly identical to that measured in 1968 by OGO-5. During the period of our investigation we observe quiet time increases in the electron flux which are of Jovian origin. These increases are restricted to energies below about 25 MeV but appear to have an energy dependence that peaks around 15 MeV.

Evenson, P.↗