AMS Applications in Nuclear Astrophysics: New Results for ¹³C(n,γ) ¹⁴C and ¹⁴N(n,p) ¹⁴C

Abstract

Abstract:The technique of accelerator mass spectrometry (AMS) offers a complementary tool for studying long-lived radionuclides in nuclear astrophysics: (1) as a tool for investigating nucleosynthesis in the laboratory; and (2) via a direct search of live long-lived radionuclides in terrestrial archives as signatures of recent nearby supernova-events. A key ingredient to our understanding of nucleosynthesis is accurate crosssection data. AMS was applied for measurements of the neutron-induced cross sections 13 C(n,g) and 14 N(n,p), both leading to the long-lived radionuclide 14 C. Solid samples were irradiated at Karlsruhe Institute of Technology with neutrons closely resembling a Maxwell-Boltzmann distribution for kT ¼ 25 keV, and with neutrons of energies between 123 and 178 keV.

Accelerator mass spectrometry measurements of theC13(n,γ)C14andWallner1, Bichler2, Buczak3 et al. 2016Phys. Rev. CSelf Cite281170View full textAdd to dashboardCite

“…These test runs were also used to study whether the highly enriched 13 C sample gave rise to an enhanced AMS background compared to measurements on natural graphite (which is assumed to be 14 C-free). It could be demonstrated that the amount of 14 C produced in the activations at keV neutron energies was high enough that this background did not jeopardize the final uncertainties [38,43,44].…”

“…The list of reaction products of interest for astrophysics includes radioisotopes over the entire mass range, e.g., 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 55 244 Pu. The present AMS measurements have been performed at the Vienna Environmental Research Accelerator (VERA) which represents a state-of-the-art AMS facility based on a 3-MV tandem [42,43]. A schematic view of the VERA facility is shown in Fig.…”

High-sensitivity isobar-free AMS measurements and reference materials for 55Fe, 68Ge and 202gPb

“…Recently, we have applied AMS for studying the production of 55 Fe in stellar nucleosynthesis [5,13,14]. Additional applications comprise detailed studies of 55 Fe production in a fusion environment: via fast neutron induced reactions on 58 Ni and 56 Fe, 55 Fe is produced through (n,a) and (n,2n) reactions, respectively [6,15].…”

“…Such conditions are achieved if the isobar does not form stable negative ions either as an atomic ion or as a suitably-chosen molecular species; well-known examples are e.g. analyzing 14 C À , 26 Al À , 129 I À , or 41 CaH À 3 , respectively, and similarly the radioisotopes in the mass range above Pb.…”

Stellar neutron capture rates – key data for thesprocess

“…This discrepancy, which is important for the role of 13 C as an s-process neutron poison, was studied using the activation technique [53]. The samples were irradiated at the Karlsruhe Institute of Technology in the quasi-stellar neutron spectrum for the direct determination of the MACS at kT = 25 keV, and also using neutron spectra with 123 and 178 keV mean energy to investigate the e↵ect of the 143 keV resonance.…”