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We have measured the charge-changing cross sections of 10.6 GeV/nucleon ^(197)Au nuclei interacting in targets of CH_2 (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH_2. 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 (ΔZ) from ΔZ=+1_(,80)Hg, down to approximately ΔZ=-29_(,50)Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small ΔZ and larger or the same for large ΔZ. The H partial cross sections are found to follow a power law in ΔZ 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 ΔZ greater than two. In the heavier targets, the cross sections for one and two proton removal have significant 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 Z_T^(1.75±0.01).

We have measured the charge-changing cross sections of 10.6 GeV/nucleon ^(197)Au nuclei interacting in targets of CH2 (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH_2. 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 (ΔZ) from ΔZ=+1, _(80)Hg, down to approximately ΔZ=-29, _(50)Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small ΔZ and larger or the same for large ΔZ. The H partial cross sections are found to follow a power law in ΔZ 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 ΔZ greater than two. In the heavier targets, the cross sections for one and two proton removal have significant 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 Z__T^(1.75±0.01).

We summarize additions to our data base of charge-changing cross sections for relativistic ultraheavy nuclei interacting in targets ranging from H to Pb. We have improved parametric fits to those cross sections as functions of energy and of projectile, target, and fragment charge. At high energies, we have determined cross sections for Au projectiles at 10.6 GeV /nucleon in targets of H, CH_2, C, Al, Cu, Sn, and Pb. Compared with cross sections at 1 GeV /n, fragment production is substantially changed, especially for the H target. These changes have important implications for calculations of interstellar propagation of ultraheavy nuclei. At lower energies, we have added Kr and Ag to our list of projectiles. Analysis of these data has led to a better understanding of the systematics of these cross sections, hence more physically meaningful parameterizations for fragmentation at high energies and for charge pickup.

Measurements of the detection efficiency of a Scintillating Optical Fiber Trajectory (SOFT) detector for 660 MeV/n Carbon, Boron, Beryllium and Lithium nuclei and for 300 MeV/n Fe nuclei are described. Detection efficiencies of 99.8%, 98.7%, 97.5%, and 93.8% for C, B, Be, and Li respectively were obtained for a single layer of fibers at an angle of incidence of 30°. These fibers had a black coating of extramural absorber (EMA) to optically decouple the fibers. Somewhat better detection efficiencies were obtained for optically coupled fibers (no EMA). The detection efficiencies for iron nuclei were ~99.7%. We have used these results to estimate the event detection efficiencies of the fiber hodoscope which is planned for use in the Cosmic Ray Isotope Spectrometer (CRIS) (Stone, et al., 1989) experiment on the Advanced Composition Explorer (ACE). We find that for the highest energy Lithium nuclei which will stop in CRIS, the detection efficiency is about 89% for 6 plane events and about 99% for 5 plane events at 30°.

The fragmentation of 10.6 GeV/n Au in CH_2. C, Al, Cu, Sn, and Pb targets has been studied using an array of ion chambers, multi-wire proportional counters (MWPC), and Cherenkov counters. Total charge-changing cross sections were found to be monotonically increasing with target charge over cross sections measured and derived from lower energy data. Partial charge-changing cross sections yielding charge changes less than 1O were depressed from those measured at lower energy.

A definitive study of the elemental abundances of nuclei over the charge range of 20 ≤ Z ≤ 100 requires a satellite mission capable of obtaining high statistics and excellent charge resolution over the full charge range. Such a mission, utilizing an electronic instrument which is an evolution of the HEA0-3 Heavy Nuclei Experiment, is described here.

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