The Charge Spectrum and Interactions of Relativistic Heavy Nuclei in the Primary Cosmic Radiation

Abstract

The charge spectrum of relativistic heavy nuclei in the primary cosmic radiation has been investigated in a stack of nuclear emulsions exposed over Texas at a ceiling height of 136 000 ft. Charges of 601 primary and of 203 fast secondary nuclei arising from fragmentations have been determined. Using a "range" criterion to count δ rays, charge resolutions up to Z = 15 have been obtained.All of the tracks have been followed through the stack and the interaction mean free paths in emulsion and the fragmentation probabilities evaluated for individual elements up to Z = 15. Using these probabilities, the relative abundances at the top of the atmosphere were 12.7 ± 1.3% L nuclei [Formula: see text], 63.5 ± 3.5% M nuclei [Formula: see text], 13.6 ± 1.6% H3 nuclei [Formula: see text], 1.7 ± 0.5% H2 nuclei [Formula: see text], and 8.5 ± 1.4% H1 nuclei [Formula: see text]. It was found that the interaction mean free paths in emulsion of the M and H nuclei were about 10% lower than previous experimental and calculated values. The fragmentation probabilities were generally in agreement with previous determinations, except for a significantly high value for the fragmentation of H1 to L nuclei.