The Application of Nuclear Cross Section Measurements to Spallation Reactions in Cosmic Rays

Abstract

Earlier in this meeting we have heard talks on the present theoretical and experimental situation regarding our understanding of nuclear spallation reactions*. These studies have been going on for several decades, essentially ever since the availability of particle accelerators made it possible to produce such reactions artificially. As in many areas, however, one finds that what scientists are able to do in the laboratory, nature has managed to do long before, often even more efficiently or dramatically. Thus we find that high energy nuclear reactions associated with cosmic rays have been going on for millions and probably billions of years in a number of astrophysical environments. Some of the traces left by such reactions on these environments are covered in other presentations at this meeting. What we would like to deal with here are the effects and implications of nuclear transformations of the cosmic ray particles themselves, and how those transformations are simulated in the laboratory. Thus, although the majority of cosmic rays are protons and alpha particles, it is the small fraction of heavier species that we will be mainly concerned with here**. These nuclides interact with the interstellar matter (again mostly hydrogen and helium) in which they propagate, and thus can undergo nuclear reactions. For the cosmic ray physicist the effects of these reactions are both favourable and unfavourable.