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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Modulation of low-energy galactic cosmic rays over the present solar cycle

Explorer satellite observations of modulations in the cosmic ray spectrum during the entire period of the solar cycle show intensity variations in the proton and alpha modulated spectra. A positive correlation between plasma density and variation in cosmic ray intensity is found that breaks during the transition period when higher energy intensity is decreasing as the solar activity increases. It is suggested that the alpha particles lead the proton particles during transition periods and thus make the lag time shorter for high rigidity near the solar maximum and the solar minimum.

Vanhollebeke, M. A.↗
NASA NTRS1972

A target design for irradiation of NaI at high beam current.

A solution to the targetry problems encountered when the iodine nucleus is a target for cyclotron irradiation is given as a new target design. A target based on this design has been used in 30 microampere irradiations of 46 MeV alpha particles for one-half hour without significant damage. Such an irradiation produces 6 to 7 mCi of Cs-129, an isotope useful in nuclear medicine. This target should also be considered for cyclotron production of the radioisotopes Cs-127, I-123, and Xe-127.

Blue, J. W.↗
NASA NTRS1973

Lunar composition from Apollo orbital measurements.

Several spectrometers carried in the Service Module of the Apollo 15 and Apollo 16 spacecraft were employed for the compositional mapping of the lunar surface. The observations involved the measurements of secondary (fluorescent) X-rays, gamma-rays and alpha particle emissions. A large scale compositional map of over 20 percent of the lunar surface was obtained for the first time. It was possible to demonstrate interesting chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the moon's hidden side.

Adler, I.↗
NASA NTRS1973

Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays.

Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra in the energy range from about 10 to the minus 8th to about 100,000 MeV at various depths in the atmosphere were calculated by using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron leakage spectrum at the particular latitude considered support the theory that the cosmic ray albedo neutron decay (Crand) mechanism is the source of the protons trapped in the inner radiation belt.

Armstrong, T. W.↗
NASA NTRS1973

Apollo 15 and 16 results of the integrated geochemical experiment.

A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface. The observations involved measurements of secondary (fluorescent) X-rays, gamma rays and alpha particle emissions. A large scale compositional map of over 20% of the lunar surface was obtained for the first time. It was possible to demonstrate significant chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the moon's hidden side.

Adler, I.↗
NASA NTRS1974

Compact source of soft X-rays

Sources of soft X-rays uses alpha particles to fluoresce light elements such as boron, carbon, and magnesium. X-ray wavelengths are varied by changing target. Technique supplies broad range of monoenergetic X-rays whose energy can be adjusted very easily.

Gorenstein, P.↗
NASA NTRS1974

Solar He-3: Information from nuclear reactions in flares

Information on solar He-3 from nuclear reactions in flares was considered. Consideration was also given to the development of models for these reactions as well as the abundance of He-3 in the photosphere. Data show that abundances may be explained by nuclear reactions of flare acceleration protons and alpha particles with the ambient atmosphere, provided that various assumptions are made on the directionality of the interacting beams and acceleration of the particles after production.

Ramaty, R.↗
NASA NTRS1974

Origin of cosmic rays

A model is presented in which cosmic electrons are produced by pulsars, and cosmic protons and alpha particles are accelerated by shock waves in supernova envelopes. It is argued that neither mechanism by itself can produce both the observed protons and electrons at energies above a few hundred MeV. But supernova accelerated electrons could constitute the majority of cosmic electrons with energy below about 10 MeV.

Cohen, J. M.↗
NASA NTRS1973

Effects of solar wind composition, anisotropy, and streaming on ordinary mode electromagnetic instability

The stability of the low-frequency waves propagating transverse to the magnetic field of a plasma composed of electrons, protons, and alpha particles with anisotropic electron and ion temperatures is explored. The threshold for the ordinary mode instability and the growth rates have a very strong dependence on the electron temperature anisotropy but have a comparatively weaker dependence on the ion temperature anisotropy, on the relative abundance of helium to hydrogen, and on the relative streaming of two ion species. The threshold for the instability of these low-frequency waves is (m sub e/m sub p) to the 1/2 power times smaller than the one corresponding to high-frequency waves; however, for a relative abundance of helium to hydrogen up to 20% for the relevant known magnetic fields, particle densities, temperatures, and drifts, the solar wind remains below the threshold for this instability.

Buti, B.↗
NASA NTRS1973

Some correlations between measurements by the Apollo gamma-ray spectrometer and other lunar observations

Observations by the Apollo 15 and 16 gamma-ray spectrometers are compared with those of a number of other experiments, both compositional and noncompositional. A general correspondence with topography is seen. The Van de Graaff area is a unique farside region with respect to observations by the laser altimeter, the subsatellite magnetometer, and the gamma-ray spectrometer. X-ray and alpha particle orbital measurements show a broad general agreement with gamma-ray data, although results from additional elements in the gamma-ray spectrum are needed to extend the comparison with X-ray data. A comparison of Th concentrations with those found at various landing sites shows generally good agreement, with the orbital values tending to be somewhat higher.

Trombka, J. I.↗
NASA NTRS1974

Observations of He I 584 A nighttime radiation - Evidence for an interstellar source of neutral helium

The intensity and spatial variations of the He I 584 A radiation in the night sky were measured to an altitude of 264 km from a sounding rocket launched from Thumba, India. The flux varied in intensity with look angle from a high of 16 plus or minus 5 rayleighs to a low of less than 1 rayleigh. The data obtained are presented in the form of an all-sky map. Since the peak flux levels observed are approximately two orders of magnitude larger than that expected from geocoronal resonant scattering, we have compared our results with those expected from two interplanetary sources of neutral helium: the penetration of the local interstellar medium into the solar neighborhood and the dust deionization of solar-wind alpha particles. The dust deionization-model predictions using currently accepted input parameters appear to be inconsistent with the observations. The interstellar helium source is compatible with the data to within the uncertainties of the models.

Paresce, F.↗
NASA NTRS1974

Post-shock spikes - A new feature of proton and alpha enhancements associated with an interplanetary shock wave

Description of the salient characteristics of temporal variations of greater than or about equal to 100 keV/nucleon protons and alpha particles during a ten-hour period associated with the passage of an interplanetary shock wave. In addition to extending measurements to energies considerably below previous observations for energetic storm particle and shock-spike events, the discovery of a new low energy feature, referred to as 'postshock spikes', is reported. The typical width of these spikes is several minutes, but they occur several hours after the passage of the shock front. Evidence is presented that spikes depends on the energy per charge of the particles.

Gloeckler, G.↗
NASA NTRS1975

Background estimation in a (gnu e)-diffusion detector

Background conditions for detecting (gamma e)-diffusion are discussed with reference to the utilization of a hodoscope system consisting of wide area flat Geiger counters connected for coincidence and of a controllable spark chamber. When calculating the background, any organic compounds synthesized from C, O2 and H2 with radioactive admixtures is presumed to be the preferrable material for the construction of the detector. The number of background events simulating the effect sought is estimated by analyzing the spectrum of the organic glass gamma radiation caused by disintegration and fission of long lived isotopes and by nuclear reactions with the participation of alpha particles and neutrons.

Glotov, V. I.↗
NASA NTRS1975

The growth of deactivated layers on CsI(Na) scintillating crystals

An effective and sensitive measurement of the depth of a deactivated or dead layer can be obtained from the relative attenuation of the 22.162 KeV and 87.9 KeV X-rays emitted by Cd 109. The alpha-particles emitted by Am 241 are also useful in measuring dead layers less than 25 microns. The properties and temporal development of dead layers are discussed in detail. The rate of growth of a deal layer is closely related to the ambient humidity, and the damage to the crystal is irreversible by any known process. The dead layer can be minimized by polishing all crystal surfaces and by keeping the crystal in a vacuum or a dry atmosphere. Since a dead layer seriously inhibits the response of a crystal to X-rays of energies below approximately 20 keV, CsI(Na) detectors should not be used at these energies unless precautions are taken to ensure that no dead layer forms.

Goodman, N. B.↗
NASA NTRS1975

Interaction between heavier ions and ring current protons

The interaction of thermal oxygen or helium ions and ring current protons may produce a wide variety of phenomena in the magnetosphere. These include the production of energetic oxygen ions or energetic helium ions, modification of the bulge region in the afternoon plasmasphere, heating of electrons in the upper ionosphere and production of stable auroral red arcs, precipitation of energetic protons, and precipitation of energetic alpha particles. Large-amplitude waves generated in the interaction may also lead to wave-wave coupling. The theory developed also suggests that heavier ions such as lithium artificially injected into the ring current to remove ring current protons may be heated substantially in the process. Computations of wave growth have been made for the first time by using measured ring current flux and anisotropies.

Brice, N.↗
NASA NTRS1975

Lasers from fission

The feasibility of the nuclear pumping of lasers was demonstrated in three experiments conducted independently at three different laboratories. In this context nuclear pumping of lasers is understood to be the excitation of a laser by the kinetic energy of the fission fragments only. A description is given of research concerned with the use of nuclear energy for the excitation of gas lasers. Experimental work was supplemented by theoretical research. Attention is given to a nuclear pumped He-Xe laser, a nuclear pumped CO laser, and a neon-nitrogen laser pumped by alpha particles. Studies involving uranium hexafluoride admixture to laser media are discussed along with research on uranium hexafluoride-fueled reactors.

Schneider, R. T.↗
NASA NTRS1975

The search for the cause of the low albedo of the moon

Experimentation concerning lunar weathering and its effect on the albedo of the surface cover consisted of: (1) determination of the surface chemical composition of lunar soil and ground-up rock samples by Auger electron spectroscopy, (2) measurement of the optical albedo of these samples, and (3) proton or alpha-particle irradiation of terrestrial rock chips and rock powders and of ground-up lunar rock samples in order to determine the optical and surface chemical effect of simulated solar wind.

Gold, T.↗
NASA NTRS1975

Plasma wave interactions with energetic ions near the magnetic equator

An intense band of electromagnetic noise is frequently observed near the magnetic equatorial plane at radial distance from about 2 to 5 Re. Recent wideband wave-form measurements with the IMP-6 and Hawkeye-1 satellites have shown that the equatorial noise consists of a complex superposition of many harmonically spaced lines. Several distinctly different frequency spacings are often evident in the same spectrum. The frequency spacing typically ranges from a few Hz to a few tens of Hz. It is suggested that these waves are interacting with energetic protons, alpha particles, and other heavy ions trapped near the magnetic equator. The possible role these waves play in controlling the distribution of the energetic ions is considered.

Gurnett, D. A.↗