R. Rosel

Simulation and modelling of the interaction of galactic protons with stony meteoroids

Abstract Stable and radioactive products of cosmic ray interactions with extraterrestrial matter provide a record of the history of small bodies in the solar system and of the cosmic radiation itself. A basis for an improved understanding of these cosmogenic nuclides was laid out in a recent experiment at Laboratoire National Saturne, by which an artificial stony meteoroid was irradiated with 1.6 GeV protons in order to simulate the exposure of meteoroids to galactic cosmic ray particles. Results for the production of 10Be, 22Na and 26Al are given. The modelling of the experimental data by a thin-target approach is described. The impact of results and analysis of the simulation experiment on model calculations of cosmogenic nuclide production rates in stony meteoroids is discussed in detail, taking 10Be production rates and their relations to those of other cosmogenic nuclides as an example.

Production of residual nuclei by α-induced reactions on C, N, O, Mg, Al and Si up to 170 MeV

Abstract In order to provide thin-target cross sections as a basis for model calculations of the interactions of solar and galactic α-particles, irradiation experiments with α-particles were performed at the injector cyclotron at PSI/Villigen ( E max = 119.7 MeV) and at the isochronous cyclotron JULIC at KFA Julich ( E max = 170.5 MeV). The stacked foil technique was used to investigate residual nuclide production from C, N, O, Mg, Al and Si. The product nuclides 7 Be, 22 Na, 24 Na and 28 Mg were measured by γ-spectrometry, 10 Be and 26 Al by accelerator mass spectrometry. The new data are compared with earlier measurements and analyzed using hybrid model of preequilibrium reactions.

Simulation of the interactions of galactic cosmic ray protons by irradiation of a thick stony target with 1.6 GeV protons

A thick spherical target (R=25 cm) made of gabbro was irradiated isotropically with 1.6 GeV protons at the Saturne cyclotron at Laboratoire National Saturne (LNS)/CEN Saclay in order to simulate the interaction of galactic cosmic ray (GCR) protons with meteoroids in space. During a 2 weeks irradiation a proton-dose of 1.32 · 1014 cm−2 was received, which is equivalent to a cosmic-ray exposure age of 1.4 Ma. Production rates were measured by X- and gamma-spectrometry, by low-level counting and by conventional and accelerator mass spectrometry (AMS). Up to now, more than 200 target-product combinations were investigated. Theoretical production rates were derived on the basis of spectra of primary protons, secondary protons and secondary neutrons calculated by Monte Carlo techniques and thin-target cross sections of the underlying nuclear reactions. The model calculations excellently describe the production depth profiles in the artificial meteoroid, if reliable crosss sections are available. The thus validated model calculations allow for the interpretation of cosmogenic nuclide abundances in stony meteorites and lunar samples in terms of their exposure history and of the history of the radiation itself.

Cross Sections of p-Induced Reactions up to 100 MeV for the Interpretation of Solar Cosmic Ray Produced Nuclides

Integral excitation functions for the production of residual nuclides by proton-induced reactions are the basic data for an accurate modelling of the interactions of solar cosmic ray particles with terrestrial and extraterrestrial matter. In order to improve the still insufficient data base, cross sections were measured for for nuclear reactions of protons up to 100 MeV on 18 elements. Using the stacked foil technique, irradiation experiments were performed at an external beam of the cyclotron at the Svedberg Laboratory/Uppsala. Radioactive residual nuclide production was measured by X- and gamma-spectrometry and by accelerator mass spectrometry for more than 120 target/product combinations. Here, cross sections for the production of 7Be from C, N, O, and Si and of 22Na and 26Al from Mg and Si are presented and discussed with respect to those from earlier work.

Production of 7Be, 10Be and 26Al by 4He-Induced Reactions Up to 171 MeV

4He-induced reactions significantly contribute to the production of cosmogenic nuclides in terrestrial and extraterrestrial matter. The cross sections of these reactions are still poorly known. Therefore, irradiation experiments with 4He were performed with energies of 119.7 MeV and 170.5 MeV in order to investigate the production of residual nuclei by 4He-induced reactions on C, N, O, Mg, Al, and Si. Here, we report on the production of 7Be, 10Be and 26Al. These nuclides were measured by gamma-spectrometry and by accelerator mass spectrometry. The new data are compared with some rare earlier measurements and analyzed by hybrid model calculations.