Measurements of the Isotopes of Lithium, Beryllium, and Boron from ACE/CRIS

Abstract

The cosmic-ray isotopes of lithium, beryllium, and boron (LiBeB) are generally believed to originate from interactions within the interstellar medium, primarily through CNO spallation. Other sources are known to contribute to the abundance of ^7Li and ^(11)B, most notably the production of ^7Li from big bang nucleosynthesis. Thus, identifying the abundances of the galactic cosmic-ray LiBeB places important constraints on the interpretations of early epoch nucleosynthesis. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring isotopic composition from helium through zinc in the energy range ˜70-500 MeV/nucleon since 1997 with high statistical accuracy. We present measurements of the isotopic abundances of LiBeB from CRIS and discuss these observations in the context of previous cosmic-ray measurements and predictions from cosmic-ray transport models.

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