Fragmentation of Relativistic Heavy Nuclei with Application to Cosmic Ray Propagation.

We have measured cross sections for charge changing interactions of several nuclei with 26 <=q Z <=q 79, at energies from 0.5 to 1.6 GeV/nucleon, on targets of C, CH_2 (and H by derivation), Al, and Cu. We summarize these measurements, which are the result of a series of experiments at the Lawrence Berkeley Laboratories Bevalac particle accelerator designed to calibrate and aid in the interpretation of the results from the High Energy Astronomical Observatory 3 Heavy Nuclei Experiment satellite instrument. The latest run is examined in detail. We have found a global expression with few free parameters for cross sections of nuclei near these energies and charges which has good chi squared values when fit to all measured cross sections. The expression is a greatly improved fit to these data compared to the standard, but much more complex, semi-empirical relations. Our experiments also indicate that unexpectedly large mass losses occur in these interactions. This result has important implications for the calculated isotopic yield from nuclear interactions near these energies and charges. We discuss application of the global fit and mass change information to the propagation of ultra-heavy cosmic rays from the source to the point of detection.