RELATIVISTIC INTERACTION OF NE-22 AND MG-26 IN HYDROGEN AND THE COSMIC-RAY IMPLICATIONS

The isotopic production cross sections for Ne-22 projectiles at 377,58 1, and 894 MeV nucleon(-1) and Mg-26 projectiles at 371 and 576 MeV nu cleon(-1) interacting in a liquid hydrogen target have been measured b y the Transport Collaboration at the Lawrence Berkeley Laboratory Heav y-Ion Spectrometer System (LBL HISS) facility. These cross sections ar e compared with those predicted by semi-empirical formulae. The system atics are studied to develop suitable inputs for calculations of galac tic cosmic-ray interstellar transport. These calculations are used to unfold the transport effects from available observations of cosmic-ray CNO isotopes to extract the underlying source composition. With these new cross section measurements, the previously reported enhancement o f O-18 at the cosmic-ray source, which is sensitive to the cross secti ons for production from Ne-22 and Mg-26 and the uncertainties in cross section prediction formulae, may be explained. There is no evidence f or an enhancement of O-18 when these new cross sections are used in a weighted slab propagation calculation.