Despite much progress,the origin of galactic cosmic-ray nuclei remains unknown.One of the more promising models for the source of these nuclei is supernova ejecta in superbubbles.In this model,supernova ejecta would be accelerated by other nearby supernovae.There is observational evidence that superbubbles have enhanced metallicity.In particular,we expect that superbubble interiors would have an enhanced abundance of actinides relative to the average interstellar medium.We discuss the expected abundance of cosmic-ray actinides in light of models of actinide yields,superbubble interiors,and interstellar medium chemical evolution.Based on these expected abundances,we calculate the expected statistics for a particular detector,the Extremely heavy Cosmic-Ray Composition Observer(ECCO),and expected confidence limits for distinguishing superbubble models from other possibilities.
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