Speaker
Description
Around half of the elements heavier than iron are produced via the slow neutron capture process ($s$-process), whereby a seed nucleus undergoes a series of neutron captures and beta decays, with the timescales of the captures being slower than those of beta decays. The $s$-process is further subdivided into several different components which occur in different types of stars. Of particular interest to this presentation is the weak $s$-process component, which occurs in massive ($>$10M$_\odot$) stars during He-core and C-shell burning, and is responsible for producing elements between mass numbers 60 and 90.
A recent study by Nishimura $et$ $al$. [1] showed that $^{77}$Se(n,$\gamma$), $^{78}$Se(n,$\gamma$) and $^{68}$Zn(n,$\gamma$) reactions have a key impact on the prediction of the $^{77}$Se and $^{78}$Se abundances, respectively, considering the current large uncertainties ($>$10% [2]) in their stellar cross sections.
Recently, $^{77}$Se, $^{78}$Se and $^{68}$Zn neutron capture cross sections have been measured at the Neutron Time-of-Flight (n_TOF) Facility at CERN, chosen for its wide spectrum of neutron energies relevant to stellar environments and high neutron energy resolution. The campaign was conducted using C$_6$D$_6$ gamma-ray detectors at the experimental area at the end of the 185-meter measurement station. The details of the experiments and subsequent analyses and results will be presented.
[1] N. Nishimura et al., Uncertainties in s-process nucleosynthesis in massive stars de-
termined by Monte Carlo variations, MNRAS 469, Issue 2, 2017
[2] I. Dillman et al., The Karlsruhe Astrophysical Database of Nucleosynthesis in Stars
Project – Status and Prospects, Nuclear Data Sheets 120, pp. 171-174, 2014