Signifiance of ultraheavy cosmic rays

The experimental composition of ultraheavy cosmic rays is compared with that expected if the cosmic-ray source had a composition like that of the solar system, or that of specific nucleosynthesis processes - the r-process or the s-process. Observations in the interval 30 < Z < 60 indicate that the cosmic-ray source is not principally r-process; rather, it looks like solar-system abundances modified by an acceleration bias correlated with the first ionization potential or modified by addition of s-process material. The abundance of actinides, which are results only of r-process, is not greatly enhanced in the cosmic rays. (orig.)