Absolute neutron capture yield calibration

Neutron physics of the Re/Os clock. I. Measurement of the (n,γ) cross sections ofOs186,187,188Mosconi1, Fujii2, Mengoni3 et al. 2010Phys. Rev. C311160View full textAdd to dashboardCite

“…The first gold resonance at 4.9 eV has been used for defining the flux in the RRR using the saturated resonance method [37]. The absolute yield normalization was determined by a fit with the R-matrix code SAMMY [38] and adopting the resonance parameters of Ref.…”

Neutron Capture Cross Section of UnstableNi63: Implications for Stellar Nucleosynthesis

“…The weak component of the astrophysical s process observed in the solar system abundance distribution includes the s-process species between Fe and Sr (60 < A < 90) [1]. Most of them are generated in massive stars during convective He core burning and convective C shell burning via the activation of the neutron source reaction 22 Neð ; nÞ 25 Mg [2][3][4][5][6]. The long-lived radioisotope 63 Ni (t 1=2 ¼ 101:2 AE 1:5 yr [7]) is located along the neutron capture path, and in typical weak s-process conditions it may become a branching point, when the neutron capture time scale is comparable with its stellar -decay rate.…”

“…In particular, at the end of He core burning the neutron source 22 Neð ; nÞ 25 Mg is activated at temperatures around 0.3 GK (GK ¼ 10 9 K), corresponding to a Maxwellian neutron energy distribution for a thermal energy of kT ¼ 26 keV. At this stage, neutron densities are too weak for a subsequent neutron capture on 63 Ni (with central peak neutron density on the order of 10 7 cm À3 , e.g., Refs.…”

“…[5,6]) and more than 90% of the 63 Ni produced decays to 63 Cu. However, the s-process material is partly reprocessed during C shell burning, where the 22 Neð ; nÞ 25 Mg neutron source is reactivated at much higher temperatures of about 1 GK, corresponding to a thermal energy of kT ¼ 90 keV.…”

“…The normalization factor was determined via the saturated resonance technique [25] in an additional run with a Au sample of the same size as the Ni sample. The Au sample was chosen such that the gold resonance at 4.9 eV is saturated, which means that all neutrons of that energy are absorbed in the sample, thus providing a measure for the absolute neutron flux at 4.9 eV.…”