Study of cosmic-ray secondary nuclei and isotopes using GALPROP

Recent high-precision measurements of the isotopic composition of beryllium in cosmic rays provide an unprecedented opportunity to study the structure of the galaxy. Due to decay processes, the ratio of radioactive isotopes to stable isotopes in cosmic rays is sensitive to the escape time of the cosmic rays during propagation. This escape time is related to the scale and physical properties of the galaxy. We examine the energy dependence of secondary cosmic ray elemental spectra and isotopic compositions, with a focus on the isotopes of beryllium. These data are considered in the context of a conventional reacceleration model, using the propagation code GALPROP to compute predicted elemental and isotopic spectra. The implications of the data on transport parameters in this conventional reacceleration model, including constraints on the diffusive halo size, are discussed.