Lead, Platinum, and Other Heavy Elements in the Primary Cosmic Radiation--HEAO-3 Results

This paper reports an observation of the abundances of cosmic-ray lead and platinum-group nuclei using data from the HEAO-3 Heavy Nuclei Experiment (HNE) which consisted of ion chambers mounted on both sides of a plastic Cherenkov counter (Binns et al., 1981). Previously we have reported on a search for actinide nuclei, Z > 88 (Binns, et al. 1982a). Further analysis with more stringent selections, inclusion of additional data, and a calibration at the LBL Bevalac, have allowed us to obtain the abundance ratio of lead and the platinum group of elements for particles that had a cutoff rigidity R_c > 5 GV.