The isotopic composition of cosmic ray B, C, N, and O nuclei

We report new high resolution measurements of the elemental and isotopic composition of galactic cosmic ray B, C, N, and O nuclei with ~ 30 to ~ 130 MeV nucleon^(-1). These observations place limits on the isotopic composition of the cosmic ray source and restrict possible models of cosmic ray origin and propagation. In particular, we find that N is significantly depleted in the cosmic ray source with respect to the solar system and local interstellar medium, a result inconsistent with models in which a majority of cosmic rays are accelerated interstellar medium material