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At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Approximations for neutron emission spectra from proton collisions between 20 and 500 MeV on nuclei of A greater than or equal to 12

When high energy protons from solar proton events or trapped radiation belts impinge on spacecraft structures, secondary particles are emitted. The most pernicious secondaries, from either a biological or physical standpoint, are the cascade and evaporation neutrons because of their reaction with matter leading to radioactive materials in the spacecraft structures. Empirically determined cascade and evaporation neutron emission spectra for protons of energy between 20 and 500 MeV incident on all materials at or above carbon in mass number are presented.

Burrell, M. O.↗
NASA NTRS1973

Radial gradients of galactic cosmic ray protons and helium nuclei

Variation of the cosmic ray intensity as a function away from the sun and its radial derivative is studied by plotting satellite cosmic ray measurements against sea level neutron monitor data. Results show that the solar modulation cavity extends well beyond 2 AU and that irregularities in the sun's magnetic field are carried outward radially by the solar wind, thus sweeping low energy cosmic rays out of the solar system and at the same time cooling cosmic rays reaching the earth.

Teegarden, B. J.↗
NASA NTRS1974

Modulation of cosmic-ray protons and helium nuclei near solar maximum

Balloon observations of proton and helium spectra in 1970, 1971 and 1972, reveal a factor of approximately 1.85 deviation from a single valued regression at low rigidities. This deviation decreases with increasing rigidity for both species. The period 1969-1970 is unique because time variations at low and high energies were anti-correlated. When satellite observations are used to extend the balloon observations to energies below 100 MeV/Nucleon, the proton spectrum showed a steeper slope in 1970 and 1972 than the characteristic J = AT spectrum observed during 1965-1969. The slope of the helium spectrum became continuously flatter during the same period (1970-1972). Computer generated spectra based on simple two parameter modulation models describe the basic features of the observations if one of the variable parameters is used to characterize the rigidity dependence of the diffusion coefficient. Models which do not allow such a variation are not consistent with the observations.

Rygg, T. A.↗
NASA NTRS1973

Comments on 'Elastically scattered recoil nuclei in solid-state detectors'

Horn and Von Oertzen (1967) have shown that tracks in mica are produced by an irradiation with 32-MeV O-16 ions. These tracks were attributed to K and Fe recoils produced by elastic scattering of the incident oxygen beam. In the present work an alternate explanation of their observations is provided. The measured characteristics of the tracks are shown to be compatible with theoretical predictions for production of tracks by inelastic (mostly compound nucleus) reactions with silicon and to be inconsistent with the previously proposed elastic scattering process. The possibility that the tracks are produced by contaminant ions in the beam cannot be ruled out.

Maurette, M.↗
NASA NTRS1974

Composition of Z greater than or equal to 5 nuclei at 1.3 GeV/n and 23 GeV/n

Measurements made with a balloon-borne counter telescope having an exposure factor of 842 sq m-ster-sec are reported. The telescope was flown from Palestine, Texas, during the fall of 1971 for a total of ten hours under an average residual atmospheric depth of 4.5 g/sq cm. The analysis indicates that the integral flux ratios above 1.3 and 23 GeV/nucleon are consistent with energy independence.

Badhwar, G. D.↗