Nuclei of the Primary Cosmic Radiation withZ≥2at High Latitudes
Abstract
A large stack of nuclear emulsions was flown on 4 September 1959, near Sioux Falls, South Dakota, at an altitude of more than 135 000 ft. The stack was flipped at altitude. Stringent scanning criteria were applied. This allowed a determination of the Li Be B flux with very small uncertainties, 971 nuclei with $Z\ensuremath{\ge}3$ were identified. The ratio $\frac{L}{M}$ nuclei is 0.51\ifmmode\pm\else\textpm\fi{}0.07 at $200 \mathrm{MeV}/N<E<700 \mathrm{MeV}/N$ and 0.32\ifmmode\pm\else\textpm\fi{}0.03 at energies >700 MeV/N. This substantial increase of light nuclei with decreasing energy is found for all light nuclei Li, Be, and B. It is concluded that the amount of material traversed by the cosmic radiation before reaching the earth is larger for the slower particles. For the rest of the elements with $Z<10$ the abundances do not change at low energies 700 MeV/N within statistics compared to results at high energies. Very little F is found at both high and low energies. C is found to be the most frequent element also below 700 MeV/N. Further results given are absolute flux values, the energy spectrum of light, medium, and heavy nuclei from 100 to 700 MeV/N and of $\ensuremath{\alpha}$ particles from 100 to 300 MeV/N. A cutoff energy of about 150 MeV/N is found for heavy primaries, much lower than the value calculated by Quenby and Wenk.
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