Ponente
Descripción
Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant and massive stars [1]. One of the best suited methods to measure neutron capture (n,γ) cross sections over the full stellar range of interest is the time-of-flight (TOF) technique. However, TOF neutron capture measurements on s-process branching isotopes are very challenging due to the limited mass (~mg) available and the high experimental background arising from the sample activity [2,3]. The situation has improved in recent years with the combination of facilities with high instantaneous flux, such as the n_TOF-EAR2 facility [4], with detection systems with an enhanced detection sensitivity and high counting rate capabilities [5,6,7]. In this context, this contribution will review recent improvements at the n_TOF facility that have allowed the first ever (n,ɣ) measurement on key isotopes such as $^{79}$Se [8], among others [9-11].
Despite the significant progresses in luminosity and detection sensitivity, the TOF technique is still not able of addressing most of the key nuclei that remain unmeasured [12]. Moreover, for some of the few measured unstable nuclei [8-11], the TOF measurement could not cover the complete neutron-energy range of astrophysical interest. In this context, complementing the TOF technique with more sensitive activation measurements in a quasi-stellar beam, when feasible, may deliver complementary or more accurate astrophysical constraints [9,12]. With this aim, n_TOF has recently deployed the new high-flux n_TOF-NEAR activation station [13]. An overview will be given on recent activities and plans at the NEAR facility, including the first (n,ɣ) activation measurement at NEAR on an unstable isotope, $^{15}$Cs, using a sample of 1.82x10¹⁵ atoms that has been just produced at ISOLDE [14]. On-going developments and future plans for challenging neutron capture measurements after CERN LS3 (>2028) will also be briefly discussed.
References
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