We report here an analysis that, for the first time, systematically normalizes the data from the HEAO 3 He~vy Nuclei Experiment on .the cosmic-ray abundances of all the elements heavier than germanium to that of .iron. In the range of atomic number Z, 33 ::;; Z ::;; 60, the analysis yields abundances of odd-even element pa1rs. These abundances are consistent with a cosmic-ray source having a composition similar to that of the solar system, but subject to so~rce. fractionation correlated with the first ionization potential (FIP) of each element. For Z > 60, the analysis yields abundances of element groups. For these heaviest nuclei, we find an enhancement of the abundance of the platinum group, elements with 74::;; Z::;; 80, relative to that in a propagated solar system source, and a corresponding increase in the abundance of the largely secondary elements in the range 62::;; Z ~ ?3. These abundances su~gest that there is an enhancement of the r-process contribution to the sour~ nucl:i m the:: Z > 60 charge region. Over the entire region of charge, standard leaky box models of propagation satisfactorily model secondary production.

Abstract-The Proton/Electron Telescope (PET) on SAMPEX is designed to provide measurements of energetic electrons and light nuclei from solar, galactic, and magnetospheric sources. PET is an all solid-state system that will measure the differential energy spectra of electrons from -1 to -30 MeV and H and He nuclei from -20 to -300 MeV/nuc, with isotope resolution of H and He extending from -20 to -80 MeVlnuc. As SAMPEX scans all local times and geomagnetic cutoffs over the course of its near-polar orbit, PET will characterize precipitating relativistic electron events during periods of declining solar activity, and it will examine whether the production rate of odd nitrogen and hydrogen molecules in the middle atmosphere by precipitating electrons is sufficient to affect 0 3 depletion. In addition, PET will complement studies of the elemental and isotopic composition of energetic heavy ( Z > 2) nuclei on SAMPEX by providing measurements of H, He, and electrons. Finally, PET has limited capability to identify energetic positrons from potential natural and man-made sources.

We have measured the charge-changing cross sections of 10.6 GeV/nucleon Au nuclei interacting in targets of CHz (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH2. The total charge-changing cross sections are higher than those measured at energies of & 1 GeV/nucleon. The measured cross sections for the heavier targets are somewhat larger than those predicted by a model based on data taken at lower energies with lighter targets. Partial charge-changing cross sections for the production of fragments from the incident Au projectiles were measured for charge changes (b, Z) from AZ = +1, soHg, down to approximately AZ = -29, SoSn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small EZ and larger or the same for large AZ. The H partial cross sections are found to follow a power law in AZ similar to that for heavier targets, instead of the exponential form observed at lower energies. Factorization is found to hold for all partial cross sections with EZ greater than two. In the heavier targets, the cross sections for one and two proton removal have signi6cant contributions from electromagnetic dissociation. The electromagnetic dissociation contribution to the total cross section is derived and found to be relatively small, but with a strong dependence on the charge of the target nuclei of the form ZT PACS number(s): 25.75.+r

Relativistic iron, lanthanum, holmium, and gold projectile nuclei with several different energies have been fragmented in targets of polyethylene, carbon, aluminum, copper, and lead. Our detectors cleanly resolve the individual charges of the heaviest of these fragments and provide some limited information on the masses. We have measured 1256 elemental partial cross sections for the production of fragments from interactions in these target materials. Values have been derived for another 417 cross sections in a hydrogen medium. These cross sections depend on the energy and mass of the projectile nuclei as well as on the nature of the target. Total charge-changing cross sections were also found, but only in a composite target, and have been shown to be weakly dependent on energy. The mean mass losses observed for fragments that have lost a few protons show that typically many neutrons are lost with each proton, producing fragment nuclei that must be highly proton rich, and consequently very unstable. The cross sections for charge pickup on heavy targets show a rapid increase with decreasing energy, particularly for the heaviest targets. The systematics of the dependencies of the partial cross sections will be discussed in a companion paper.