MEASUREMENTS OF THE RELATIVE ABUNDANCES OF HIGH-ENERGY COSMIC-RAY NUCLEI IN THE TeV/NUCLEON REGION

Abstract

We present measurements of the relative abundances of cosmic-ray nuclei in the energy range of 500-3980 GeV/ nucleon from the second flight of the Cosmic Ray Energetics And Mass balloon-borne experiment.Particle energy was determined using a sampling tungsten/scintillating-fiber calorimeter, while particle charge was identified precisely with a dual-layer silicon charge detector installed for this flight.The resulting element ratios C/O, N/O, Ne/O, Mg/O, Si/O, and Fe/O at the top of atmosphere are 0.919 0.123 stat 0.030 syst , 0.076 0.019 stat 0.013 syst , 0.115 0.031 stat 0.004 syst , 0.153 0.039 stat 0.005 syst , 0.180 0.045 stat 0.006 syst , and 0.139 0.043 stat 0.005 syst , respectively, which agree with measurements at lower energies.The source abundance of N/O is found to be 0.054 0.013 stat 0.009 syst+0.010esc-0.017. The cosmic-ray source abundances are compared to local Galactic (LG) abundances as a function of first ionization potential and as a function of condensation temperature.At high energies the trend that the cosmic-ray source abundances at large ionization potential or low condensation temperature are suppressed compared to their LG abundances continues.Therefore, the injection mechanism must be the same at TeV/nucleon energies as at the lower energies measured by HEAO-3, CRN, and TRACER.Furthermore, the cosmic-ray source abundances are compared to a mixture of 80% solar system abundances and 20% massive stellar outflow (MSO) as a function of atomic mass.The good agreement with TIGER measurements at lower energies confirms the existence of a substantial fraction of MSO material required in the TeV per nucleon region.