Isotopic composition of primary cosmic-ray nitrogen and oxygen with consequences for source models

Abstract

An experimental investigation of the isotopic composition of cosmic-ray nitrogen and oxygen is reported. The detector is a stack of nuclear emulsions exposed at about 3 g cm−2 atmospheric depth. The mass determinations are based on photometric track width measurements on stopping nuclei. The standard deviation of the mass measurements is 0.46 AMU for nitrogen and 0.50 AMU for oxygen. The energy of the measured nuclei falls in the interval 220–450 MeV nucleon−1 at the top of the atmosphere.