Implications for Cosmic Ray Propagation from ACE Measurements of Radioactive Clock Isotope Abundances

Galactic cosmic rays (GCR) interact to produce secondary fragments as they pass through the interstellar medium (ISM). Abundances of the long-lived radioactive secondaries ^(10)Be, ^(26)Al, ^(36)Cl, and ^(54)Mn can be used to a derive the confinement time of cosmic rays in the galaxy. Abundances for these species have been measured recently using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) spacecraft. To interpret this data we have modeled the production and propagation of the radioactive secondaries, taking into account recently published isotopic production cross-sections. Abundances for all species are consistent with a confinement time of π_(esc) ~22 x 10^6 years.