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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Determination of the charge of relativistic heavy nuclei from emulsion tracks

The number of delta rays with energies between 50 and 150 keV that are produced by heavy nuclei in emulsions is calculated. The Z(2) dependence predicted by the first Born approximation is corrected by a direct calculation of the Mott exact phase-shift scattering cross section. Comparisons are made with corrections predicted by the second Born approximation. When the phase-shift results are applied to the problem of charge identification, corrections of up to 4 units of charge for 1.457-GeV/nucleon nuclei with charge Z = 75 are found.

Morgan, S. H., Jr.↗
NASA NTRS1972

Frequency of light-flashes induced by Cerenkov radiation from heavy cosmic-ray nuclei

The expected frequency was calculated for light flashes induced in the dark-adapted eye by Cerenkov radiation from the flux of heavy nuclei that exists in space beyond the geomagnetic field. The expected frequency of light flashes depends on the threshold number of photons that must be absorbed in a rod cluster. The results of the calculation are presented as a curve of the mean frequency of light flashes versus the threshold number of absorbed photons. The results are not sensitive to variations in the path length from 5 to 15 grams per square centimeter of water-equivalent before the nucleus reaches the retina. Calculations were based on the fluxes and energy spectra of galactic cosmic ray nuclei of helium to iron, measured at a time of minimum solar modulation. The expected light flash frequencies induced by Cerenkov radiation are consistent with the frequencies reported by the astronauts on Apollo missions 11 through 14.

Madey, R.↗
NASA NTRS1972

Enhanced emission of iron nuclei in solar flares

A silica glass window from Apollo 12 CM and a piece of flint glass from the Surveyor 3 camera filter were examined for Fe nuclei tracks. A large difference between observed and predicted track densitites was found. At low rigidity (or energy), the solar particle Fe/He ratio is much higher than the photospheric abundance ratio, but decreases with increasing rigidity until it approaches the photospheric value at a rigidity of about 500 MV. It is felt that the low-energy Fe tracks are of solar origin. The implications that heavy nuclei can be preferentially emitted from a source of energetic particles are discussed. Other conclusions are the following: Rocks exposed on the lunar surface for 10 million yr would accumulate about 6 x 10 to the 12th power tracks/sq cm, and the rate of radiation-induced erosion is about 10 to the -9 cm/yr. The lunar soil should contain heavily irradiated small grains, some with track densities of about 10 to the 12th power/sq cm that have flaked from radiation-damaged rock surfaces and some that were irradiated while at the top of the soil layer.

Price, P. B.↗
NASA NTRS1972

The survival of heavy nuclei in cosmic ray source environments

Results from the Goddard balloon spectrometer and the results reported by Soviet scientists using the Proton series of satellites are summarized. The important experimental results from the balloon spectrometer experiment are as follows: (1) On a total-energy scale, protons constitute only a minor proportion of the cosmic rays, only 20 percent. The rest of the cosmic rays are complex nuclei. (2) All the nuclei have the same power low spectrum in total energy and so the composition seems to be independent of energy.

Balasubrahmanyan, V. K.↗
NASA NTRS1972

Application of the adiabatic-nuclei theory to vibrational excitation.

The adiabatic-nuclei theory is shown to be quantitatively applicable to vibrational excitation of diatomic molecules by electron impact. When the dependence of the fixed-nuclei phase shifts on internuclear separation is approximated by a two-term Taylor series, the resulting formulas are transparent and easily evaluated. Application to e-H2 excitation is made, phase-shift derivatives are estimated, and the theory is found to fit experimental data.

Faisal, F. H. M.↗
NASA NTRS1972

A quantitative investigation of the solar modulation of cosmic-ray protons and helium nuclei

The differential energy spectra of cosmic ray protons and He nuclei were measured at energies up to 315 MeV/nucleon using balloon-borne and satellite-borne instruments. These spectra are presented for solar quiet times for the years 1966 through 1970. The data analysis is verified by extensive accelerator calibrations of the detector systems and by calculations and measurements of the production of secondary protons in the atmosphere. The spectra of protons and He nuclei in this energy range are dominated by the solar modulation of the local interstellar spectra. Numerical solutions to the transport equation are presented for a wide range of parameters.

Garrard, T. L.↗
NASA NTRS1973

Primary and secondary nuclei in high-energy cosmic rays

Charge and particle trajectory measurements during a balloon-borne experiment observing the composition of cosmic rays, are interpreted by plotting differential intensities of various nuclei of both primary and secondary origin above 3 GeV/nucleon. The large spectral difference between carbon plus oxygen and iron is confirmed in the difference between their secondary products. This large difference cannot be explained as being solely due to propagation effects and it is concluded that preferential acceleration of heavy nuclei due to a source effect is present.

Ormes, J. F.↗
NASA NTRS1972

The preferential acceleration of heavy nuclei in solar flares.

A two-stage model is proposed for the mechanism of heavy nuclei (Z greater than 8) accelerated in solar flares. In the first stage, fully stripped ions are first accelerated to suprathermal energies. In the second stage, a fraction of these ions are Fermi-accelerated to higher energies. Transport to the Fermi-acceleration region involves electron pickup, while injection into Fermi acceleration is rigidity dependent. The degree of enhancement of the abundance of heavy nuclei may be expected to vary for each individual flare.

Cartwright, B. G.↗
NASA NTRS1973

Evidence for differences in the energy spectra of cosmic ray nuclei.

Comparison of the intensities of He, C + O, and Fe + Ni cosmic ray nuclei as measured on balloon flights in Canada and Argentina at several energy levels between about 1 and 50 GeV per nucleon. A re-analysis of previous data and those of Juliusson et al. (1972) and Smith et al. (in the press) is carried out. The differences in the spectra of these nuclei are discussed.

Webber, W. R.↗
NASA NTRS1973

Interplanetary radial gradients of galactic cosmic ray protons and helium nuclei - Pioneer 8 and 9 measurements from 0.75 to 1.10 AU.

We report measurements of the radial interplanetary cosmic ray gradient made with cosmic ray instruments aboard the Pioneer 8 and 9 spacecraft. The time period covered in these studies is from January 1968 to June 1969. During this time, the radial separation of these two spacecraft varied from 0.75 to 1.10 AU from the sun. This study includes detailed measurements of the differential spectra and gradients of protons and helium nuclei from 2 to 1200 Mev/nucleon. The differential gradient for each species is observed to go through a broad maximum of about 50%/AU at energies corresponding to about 1 BV rigidity, decreasing at both lower and higher rigidities. The proton and helium nuclei gradients are small down to the lowest energies we measure.-

Webber, W. R.↗
NASA NTRS1973

Quiet time energy spectra of heavy nuclei from 20 to 400 keV/amu

Glass track detectors were exposed to cosmic rays on the moon from December 11 to 13, 1972, during a period of relatively quiet sun activity as inferred from satellite proton counters. From 80 to 400 keV/amu, the differential flux of heavy cosmic ray nuclei decreases roughly as E to the -2nd power; this result together with the greater flux from the solar than the antisolar direction identify these nuclei as solar in origin.

Woods, R. T.↗
NASA NTRS1973

A mechanism for the abundance enhancements of heavy nuclei in solar flare particle events

A mechanism is proposed to account for the recently reported abundance enhancements of heavy nuclei in solar flares. The mechanism requires two acceleration stages for its operation: First, fully stripped ions are accelerated to suprathermal energies, and subsequently, a fraction of these ions are Fermi accelerated to higher energies. It is shown that because injection into Fermi acceleration is rigidity dependent and the ions may pick up electrons during transport to the Fermi acceleration region, an enhancement of the abundances of heavy nuclei can occur. The degree of the enhancement depends on a number of factors particular to each flare, so that the degree of enhancement may be variable from flare to flare, or may be a function of time within a given flare. In some flares, conditions may be such that no enhancement would be expected.

Cartwright, B. G.↗
NASA NTRS1974

Isotopic composition of cosmic ray nuclei with Z greater than or equal to 10

Results of measurements of the isotopic composition of Z greater than or equal to 10 cosmic ray nuclei using a new technique employing a combination of Cerenkov and total energy counters. An effective mass resolution of about 0.4 AMU is obtained for particles with energies between 400 and 500 MeV/nuc and charges between 12 and 16. The preliminary mass distribution of nuclei with charges from 12 to 28 is presented and discussed.

Webber, W. R.↗
NASA NTRS1974

Properties and synthesis of heavy nuclei and properties of neutron star matter

The nuclear Thomas-Fermi model which is based on nuclear matter calculations has been successfully applied to the study of the bulk properties of nuclei. It is ideally suited for extrapolation into the region of very neutron-rich and of superheavy nuclei. It is therefore a valuable approach for r-process calculations as well as for the study of neutron star matter at subnuclear densities.

Buchler, J. R.↗
NASA NTRS1974

The abundances of nuclei in the cosmic radiation

The relative abundances are treated as a consequence of processes in cosmic ray transport occurring during passage of the radiation through interstellar material at high velocity. Some of the subjects mentioned are nuclear fragmentation and the production of secondary nuclei, nuclear reactions, energy loss and nuclear decay, ionization, the range-energy relation and propagation variables, capture and loss of electrons, the propagation of nuclei, the transport equation, equilibrium solutions, energy-dependent path length distribution, exponential path length distributions, discrete spectra, sources, supernovae, and the origin of the abundances. The connection between the space-time features of the sources, the material traversed, and the effects of magnetic fields is established by describing the particle-field interaction as a diffusive or random-walk process.

Reames, D. V.↗
NASA NTRS1975

A measurement of abundances of VVH nuclei above 0.6 GeV per nucleon

The abundance distribution of very very heavy (VVH) nuclei just beyond the iron group has been measured with a balloon-borne counter telescope flown in 1971 and 1972. While the statistical accuracy of these observations is limited, they are of considerable interest since very little work has so far been done to determine the abundance of nuclei with charge between 27 and 36. It is found that the element distribution in the cosmic rays arriving at the top of the atmosphere is quite similar to the solar-system abundance distribution in this interval.

Juliusson, E.↗
NASA NTRS1975

The origin of the nonthermal radiation of quasi-stellar objects and galactic nuclei

The supermassive-star model for the origin of the nonthermal luminosity of quasars and nuclei of Seyfert galaxies is analyzed. In the general model, a moving magnetic field is the accelerating mechanism for ultrarelativistic particles and gravitational collapse is the energy source. Several specific models are considered for the magnetic field, including a frozen-in field that is twisted about the axis of a rotating supermassive star, a tightly wound magnetic spiral, and the rotating field of a giant pulsar. In the general model, an accelerating efficiency close to unity is assumed. However, it is found that observational and theoretical evidence indicate an accelerating efficiency of less than 0.01 for the specific magnetic-field models. Mass-loss rates of quasars and Seyfert nuclei are calculated on the basis of the lower efficiency value and found to be reasonable.

Opher, R.↗