Abstract
Cosmic Rays (CRs) are powerful tools for the investigation of the structure of the magnetic fields in the galactic halo and the properties of the Inter-Stellar Medium. There are two parameters of CR propagation models: The galactic halo (half-) thickness, H, and the diffusion coefficient, D, are loosely constrained by current CR flux measurements; in particular, a large degeneracy exists, as only H/D is well measured. The 10Be/9Be isotopic flux ratio (thanks to the 2 My lifetime of 10Be) can be used as a radioactive clock that provides the measurement of the residence time of CRs in the galaxy. This is an important tool for solving the degeneracy of H/D. Past measurements of the 10Be/9Be isotopic flux ratios in CRs are scarce, limited to low energy, and affected by large uncertainties. Here, a new technique for measuring the 10Be/9Be isotopic flux ratio in magnetic spectrometers with a data-driven approach is presented. As an example, by applying the method to beryllium events that were published by the PAMELA experiment, it is now possible to determine the important 10Be/9Be measurements while avoiding the prohibitive uncertainties coming from Monte Carlo simulations. It is shown how the accuracy of the PAMELA data permits one to infer a value of the halo thickness with a precision of up to 25%.