Cosmic-Ray Clocks

Secondary radioactive isotopes that are used for the determination of cosmic-ray age have relatively short decay lifetimes. The measured abundance of these isotopes at low energies is representative of the cosmic-ray diffusion and the gas distribution in a region of a few hundred parsecs around the Sun. We show how to determine the local cosmic-ray diffusion coefficient in the Galaxy using the data on decaying cosmic-ray nuclei. Calculated surviving fractions of decaying secondary isotopes in diffusion and leaky box models are presented.