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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

High-energy proton radiation damage of high-purity germanium detectors

Quantitative studies of radiation damage in high-purity germanium gamma-ray detectors due to high-energy charged particles have been carried out; two 1.0 cm thick planar detectors were irradiated by 6 GeV/c protons. Under proton bombardment, degradation in the energy resolution was found to begin below 7 x 10 to the 7th protons/sq cm and increased proportionately in both detectors until the experiment was terminated at a total flux of 5.7 x 10 to the 8th protons/sq cm, equivalent to about a six year exposure to cosmic-ray protons in space. At the end of the irradiation, the FWHM resolution measured at 1332 keV stood at 8.5 and 13.6 keV, with both detectors of only marginal utility as a spectrometer due to the severe tailing caused by charge trapping. Annealing these detectors after proton damage was found to be much easier than after neutron damage.

Pehl, R. H.↗
NASA NTRS1978

Prompt solar proton events and coronal mass ejections

Data from the HAO white-light coronagraph and the X-ray telescope on Skylab have been used to investigate the coronal manifestations of 18 prompt solar proton events observed on the IMP 7 spacecraft during the Skylab period. Evidence is found that a mass-ejection event is a necessary condition for the occurrence of a prompt proton event. Mass-ejection events can be observed directly in the white-light coronagraph when they occur near the limb and inferred from the presence of a long-decay X-ray event when they occur on the disk. It is suggested that: (1) the occurrence of mass-ejection events facilitates the escape of protons - whether accelerated at low or high altitudes - to the interplanetary medium; and (2) there may exist a proton acceleration region above or around the outward moving ejecta far above the flare site.

Kahler, S. W.↗
NASA NTRS1978

Characteristics of sunward flowing proton and alpha particle fluxes of moderate intensity

The diffusive streaming of low-energy protons has been found to be predominately toward the sun during periods between prompt solar particle events. This occurs for essentially all solar wind velocities and proton intensities. The average radial component of this anisotropy (14%) and its dependence on the solar wind velocity agree with values found by a steady-state propagation model. The average radial component (16%) of the diffusive flow of low-energy alpha particles is similar to that observed for protons, suggesting a common origin. The sunward diffusion of alpha particles and protons indicates that these slightly enhanced fluxes contain a positive radial gradient. The direction of the diffusive anisotropy is a function of the magnetic field direction.

Marshall, F. E.↗
NASA NTRS1979

A query into the source of proton emission from solar flares, report 2

Seven solar flares that were followed by major proton events were examined to determine the diverse and common properties of major flares. The most probable site of primary proton acceleration is cospatial with the site and instant of formation of coronal loops. Because loop formation occurs through the entire duration of major solar flares over significantly large areas of active centers, it is proposed that proton injection occurs from a relatively large volume of space in the corona of active centers and is continuous throughout, and possibly even after, the visible duration of the related chromospheric flare. The flare veil is hypothesized to occur as a result of proton charge exchange taking place in the white-light transient. The Kopp and Pneuman model of loop formation by magnetic reconnection is suggested as an adequate and satisfactory model for all major flares with the provision that the beginning of rapid magnetic field reconnection is coincident with flare start.

Martin, S. F.↗
NASA NTRS1978

Simultaneous measurements of energetic protons and electrons in the distant magnetosheath, magnetotail, and upstream in the solar wind

The paper investigates the presence of energetic protons and electrons in the magnetopause/magnetosheath region of the tail as well as upstream from the bow shock in the solar wind, estimates the energy densities of protons and electrons, and assesses the relationship between the energies associated with these particles and the dayside reconnection region. The study is based on measurements in experiments on the IMP 7 and 8 spacecraft. It is shown that the energetic protons and electrons are present not only in the distant magnetosheath but also in the upstream solar wind and inside the magnetosphere. These protons carry much more energy (x50) than the electrons, and most likely originate inside the magnetosphere. Thus there appears to be little connection between the presence of these energetic particles in the distant magnetosheath region and the dayside reconnection region.

Krimigis, S. M.↗
NASA NTRS1979

Anisotropies in the fluxes of Pioneer 10 protons

One-hour-averaged fluxes of 1.8- to 2.15-MeV protons observed by the LET2 detector on Pioneer 10 on the inbound trajectory showed anisotropies attributable to corotation of Jupiter's magnetodisc only when Pioneer was near the dipole equator. Most of the time the anisotropy greatly exceeded the value expected from corotation. Gradients in the distribution function can be used to account for this excess anisotropy, but the amount of gradient required is unacceptably large by 1-2 orders of magnitude. If they were taken as real, these gradients would predict almost complete disappearance of these protons from Jupiter's magnetosphere in a matter of hours. The remedy is to introduce into the model of the distribution function proton flow along field lines away from the equator into both the southern and the northern hemisphere. The parallel flux at the southernmost latitudes reached by Pioneer can reach 25% of the product of proton density and velocity, i.e., 25% of the maximum possible.

Northrop, T. G.↗
NASA NTRS1978

An estimation of the primary proton spectrum between 10 to the 12th and 10 to the 14th eV

Based on measurements of unaccompanied charged hadron flux from 10 to the 11th to 10 to the 14th eV at mountain altitudes, the primary proton flux is estimated using recently determined proton-proton total cross sections from new measurements of the real part of the forward scattering amplitude at ISR, and Glauber theory to calculate proton-air inelastic cross section. The derived spectrum agrees well with extrapolation of the direct measurements below 2 times 10 to the 12th eV without change of slope.

Gaisser, T. K.↗
NASA NTRS1980

Instability of equatorial protons in Jupiter's mid-magnetosphere

Two different models for the distribution function are fit to the Jovian protons seen by Pioneer 10 inbound. The models reproduce the observed energy and angular distributions. These models are then used to assess the collisionless mirror instability. Because of the pancake proton angular distributions in the equatorial ring current region, the ring current particle population appears to be mirror unstable at times, with instability growth rates of about 10 min. Such a time is consistent with observed proton flux autocorrelation times. An instability such as this (there are other candidates) may be responsible for the previously established proton flux flowing parallel to the magnetic field away from the equatorial region.

Northrop, T. G.↗
NASA NTRS1981

Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements

The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.

Witt, N.↗
NASA NTRS1981

Several features of the earthward and tailward streaming of energetic protons /0.29-0.5 MeV/ in the earth's plasma sheet

The reported investigation represents an extension of a study conducted by Lui and Krimigis (1981) who have examined the question of transport of energetic protons measured by the Charged Particle Measurements Experiment on IMP 7 and 8 in the magnetotail. It has been shown that there is a substantial net earthward transport of these particles, with fluxes seemingly capable of replenishing the losses of outer radiation belt protons. In the current investigation the earlier study is extended by reporting several features of the earthward and tailward streaming of these energetic protons. Attention is given to selection criteria and isolation of magnetospheric protons, the dawn-dusk reversal in streaming anisotropy, the amplitude of streaming anisotropy, and spectral hardness.

Lui, A. T. Y.↗
NASA NTRS1981

Effects of low temperature periodic annealing on the deep-level defects in 200 keV proton irradiated AlGaAs-GaAs solar cells

The GaAs solar cell has shown good potential for space applications. However, degradation in performance occurred when the cells were irradiated by high energy electrons and protons in the space environment. The considered investigation is concerned with the effect of periodic thermal annealing on the deep-level defects induced by the 200 keV protons in the AlGaAs-GaAs solar cells. Protons at a fluence of 10 to the 11th P/sq cm were used in the irradiation cycle, while annealing temperatures of 200 C (for 24 hours), 300 C (six hours), and 400 C (six hours) were employed. The most likely candidate for the E(c) -0.71 eV electron trap observed in the 200 keV proton irradiated samples may be due to GaAs antisite, while the observed E(v) +0.18 eV hole trap has been attributed to the gallium vacancy related defect. The obtained results show that periodic annealing in the considered case does not offer any advantages over the one time annealing process.

Li, S. S.↗
NASA NTRS1981

Search for effect of longitudinally polarized protons on optically active amino acids

The influence of irradiation by longitudinally polarized protons on the differential decomposition of amino acid is investigated in a test of the Vester Ulbricht hypothesis that L-amino acids were produced in preference to the D isomers on the primitive earth due to the effects of parity violation in beta decay. Samples of DL-leucine were irradiated with protons of both positive and negative longitudinal polarization, then analyzed by gas chromatography. Despite advantages of higher polarization, lower velocity and higher ionization density of protons with respect to electrons, proton irradation is found to lead to no detectable asymmetries in DL-leucine degradation, even at 50% gross degradation.

Lemmon, R. M.↗
NASA NTRS1982

Solar wind protons - Three-dimensional velocity distributions and derived plasma parameters measured between 0.3 and 1 AU

Such nonthermal features as temperature anisotropies, heat fluxes, and proton double streams have been observed by a Helios solar probe survey of solar wind three-dimensional proton velocity distributions between 0.3 and 1 AU. It is found that a strong anisotropy in the core of proton distributions, with a temperature that is larger perpendicular rather than parallel to the magnetic field, is a persistent feature of high-speed streams, becoming most pronounced in the perihelion, or about 0.3 AU. Isotropic distributions have been detected only close to, and at, magnetic sector boundaries, and the flattest radial temperature profiles are found in high-speed streams. These observations indicate that local heating or proton heat conduction occurs in the solar wind.

Marsch, E.↗
NASA NTRS1982

Solar flares, proton showers, and the Space Shuttle

Attention is given the hazards posed to Space Shuttle crews by energetic proton radiation from inherently unpredictable solar flares, such as that of April 10-13, 1981, which was experienced by the Space Shuttle Columbia. The most energetic protons from this flare reached the earth's atmosphere an hour after flare onset, and would have posed a potentially lethal threat to astronauts engaged in extravehicular activity in a polar or geosynchronous orbit rather than the low-latitude, low-altitude orbit of this mission. It is shown that proton-producing flares are associated with energization in shocks, many of which are driven by coronal mass ejections. Insights gained from the Solar Maximum Year programs allow reconsideration of proton shower forecasting, which will be essential in the prediction of the weather that Space Shuttle astronauts will encounter during extravehicular activities.

Rust, D. M.↗
NASA NTRS1982

The dependence of single event upset on proton energy /15-590 MeV/

Low earth orbit satellite and Jupiter orbiter probe semiconductor devices may incur soft errors or single event upsets, manifested as bit flips, during exposure to such nuclear particles or heavy ions as trapped protons with energies ranging up to 1000 MeV. Experimental data is given on the average proton fluence needed to cause a bit flip as a function of proton energy for isoplanar bipolar TTL RAMs. Error dependence data shape and threshold energy can be related to the existing body of theoretical data on energy deposition following proton nuclear reactions. Experimental data also show that the relative cross sectional amplitude for functionally identical devices can be related to the device's power consumption.

Nichols, D. K.↗
NASA NTRS1983

Evolution of electron and proton temperatures in a flaring loop. I - A case of thermal heating of electrons

A temperature difference between electrons and protons produced in a flaring loop was investigated experimentally by adopting a one-fluid, two-temperature model instead of a single-temperature model. Consideration was given to the case in which flare energy is released in the form of heating of electrons located in the top part of the loop. In this case, a large temperature difference appears in the corona in the energy-input phase of the flare. When the material evaporated from the chromosphere fills the corona, the temperature difference in the loop begins to shrink rapidly from below. Eventually, in the loop apex, the proton temperature exceeds the electron temperature mainly due to cooling of the electrons by conduction down the loop and heating of the protons by compression of the ascending material. In the late phase of the flare (about 15 min from the flare onset), the temperature difference becomes less than 2 pct of the mean temperature of electrons and protons at every point in the loop.

Nagai, F.↗
NASA NTRS1983

Studies of Neutron and Proton Nuclear Activation in Low-Earth Orbit 2

The study of neutron and proton nuclear activation in low-Earth orbit reported in NASA CR-162051 has been continued with increasing emphasis given to primary and secondary neutron activation. The previously reported activation due to protons has been modified to include: (1) flux attenuation caused by all inelastic reactions; (2) the modification of the proton flux distribution caused by sample covering material; and (3) the activation of the sample as a function of the distance into the sample from the surface of incidence. A method has been developed for including the effects on the activation of the finite width and length of the samples. The reactant product spectra produced by proton-induced reactions has been studied. Cross sections needed for neutron induced reactions leading to long-lived (half-life 1 day) radioisotopes have been identified and, in some cases, compiled.

Laird, C. E.↗
NASA NTRS1985

Electrons and cosmic ray produced protons in Saturn's inner magnetosphere

The Cerenkov detector on Pioneer 11 previously observed Crand protons above 600 MeV in Saturn's inner magnetosphere, mixed with a poorly understood background of energetic electrons. The electron count is separated from the proton counts and the first-order angular distributions are established for each species. To do this the theoretical relationships among the harmonic coefficients of the count rate is used as a function of spacecraft roll angle. The majority of the counts were electrons with energy above several MeV; i.e., with drift periods shorter than the satellite orbital resonance. The electrons have isotropic pitch angle distributions, and the protons pancake over most of the region between Mimas and the rings, although there is a small region of dumbbell proton distributions in the vicinity of Janus and epimetheus.

Northrop, T. G.↗