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The Properties of Cosmic Radiation at Very High Altitudes
Phys. Rev. 75, 69 – Published 1 January, 1949
DOI: https://doi.org/10.1103/PhysRev.75.69
Abstract
The variation of the vertical cosmic-ray intensity as a function of altitude has been investigated in a series of free-balloon ascents with standardized quadruple-coincidence-counter trains containing various amounts of interposed absorber, to a maximum thickness of 7.5 cm Pb. The curves thus obtained converge at the "top of the atmosphere." A maximum occurs in the curve with 4 cm of Pb, but disappears with 6 cm of Pb. Cosmic-ray absorption curves at various altitudes above that corresponding to an atmospheric pressure of 250 mm of Hg are plotted from the data, as are integral and differential distributions-in-range. The relative stopping powers of carbon and lead are also available from the data.
Disturbing effects such as those arising from side showers and scattering appear to be negligible. An extrapolation procedure, which leads to results consistent with those of other experiments, provides a new picture of the composition of the cosmic rays in the atmosphere. With heavier particles () displaying a maximum intensity at a higher altitude than electrons (), the conclusions drawn from the present investigation are compatible with a primary radiation consisting of protons (and possibly heavier nuclear particles) producing mesotrons which subsequently give rise to the electronic component.
Comparison of the results reported here with those of Schein and Allen indicate an absorption of primaries, by a process other than ionization, in thicknesses of Pb between 7.5 and 18 cm.
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