Xenon production cross sections at intermediate energies and production rates in small meteoroids based on simulation experiments

Abstract

Thin-target production cross sections of xenon isotopes from barium were determined at proton energies of 600 MeV, 800 MeV, 1200 MeV and 2600 MeV using the CERN synchrocyclotron, LANL/Los Alamos and LNS/Saclay accelerators. The data thus obtained are compared with a priori thin-target production cross section calculations using code ALICE. Production cross sections for the neutron induced reactions are estimated theoretically. Together with the cross sections at low energies (≤45 MeV) for the p-induced reactions on barium, determined by us earlier, the present data set provides a basis for evaluating the cosmogenic xenon production rates in extraterrestrial matter. Further, the depth profiles for the production of stable xenon isotopes and 127Xe radionuclide in 5 cm, 15 cm and 25 cm artificial meteoroids, irradiated isotropically with 600 MeV protons, are determined experimentally. These measured depth profiles are compared with theoretical estimates of the xenon production rates from barium in artificial meteoroids, calculated by folding depth dependent spectra of primary protons, secondary protons and neutrons with the thin-target excitation functions for the underlying proton and neutron induced reactions. The production rates thus obtained are compared with theoretical estimates using the depth profiles of well studied radionuclide production in meteoroids of various sizes. The measured xenon production ratios in the thick targets isotropically irradiated with 600 MeV protons and the calculated xenon production ratios in artificial meteoroids irradiated with realistic GCR energy spectrum are compared with those deduced from meteorite analysis and are found to be significantly different. The possible reasons for the discrepancy are explored. The refinements that are still necessary to accurately estimate xenon production rates in extraterrestrial material are discussed.