Charge Composition and Energy Spectra of Cosmic-Ray Nuclei at Energies above 20 GeV Per Nucleon

An instrument to measure the charge composition and energy spectra of cosmic-ray nuclei of charge Z = 3 and above has been exposed for a net total of 7.6 m2 sr hours in three balloon flights during 1971 and 1972. The instrument is a scintillation-Cerenkoy counter telescope, including two gas Cerenkov counters for energy measurements above 20 GeV per nucleon, and up to about 100 GeY per nucleon. In this paper we present the charge composition and energy spectra that have been measured in that energy range. The nuclear composition has been found to change with energy. The flux of nuclei produced by spallation of source nuclei in the Galaxy has been found to decrease faster with increasing energy than the flux of source nuclei. The carbon to oxygen ratio measured above 20 GeV is significantly lower than measured at low energy. Iron exhibits a flatter energy spectrum than other nuclei. The results are interpreted as showing that the high-energy nuclei have traversed less material than the low-energy nuclei. Subject heading: cosmic rays

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