Stellar 78,80,84,86Kr(n,γ) Reactions Studied by Activation at SARAF-LiLiT, Atom Trap Trace Analysis and Decay Counting

Abstract

We report on (n,γ) neutron capture experiments performed with the Liquid-Lithium Target (LiLiT) and the mA-proton beam at 1.92 MeV (2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF). The setup yields high-intensity 30-keV quasi-Maxwellian neutrons (3-5 × 1010 n/s) closely reproducing the conditions of s-process stellar nucleosynthesis. The 78,80,8486Kr(n,γ) reactions at the border between weak- and strong- s-process were studied. A Ti sphere filled with 107.7 mg of natural Kr gas was placed in an irradiation chamber downstream of LiLiT with a gold foil used as a neutron fluence monitor during the activation. The activities of the short-lived Kr isotopes (7985m87Kr) were measured by γ decay counting with a HPGe detector. The long-lived Kr isotopes (81,85gKr) were measured by atom counting via Atom Trap Trace Analysis (ATTA) at Argonne and Low-Level Counting (LLC) at Bern.