Speaker
Alvaro Tolosa Delgado
(IFIC (Instituto de Fisica Corpuscular))
Description
The distribution of solar system elemental abundances, after correction for s-process contributions, shows a maximum around A ∼ 80 sometimes called the 1 st r-process abundance peak. However the origin of the elements contributing to this peak is uncertain and several astrophysical processes have been proposed. Observations in ancient ultra metal poor stars [1] indicate that other mechanisms contribute here and may be even dominant [2]. We consider here a weak r-process [3], which can occur in core-collapse supernova events [4] or neutron star mergers [5]. Sensitivity studies [6] indicate the need to measure half-lives T_1/2 and neutron emission probabilities Pn for neutron-rich nuclei in this region, as the prediction of different theoretical alculations disagree significantly, and these quantities shape the final abundance distributions.
The BRIKEN project was launched to expand our knowledge on T 1/2 and P n values to not-yet-accessed very neutron-rich nuclei over the entire nuclear chart, that are important for r-process abundance calculations. It exploits the very large beam intensities of the RIBF facility at RIKEN [7] and the selection capability of the BigRIPS in-flight separator [8] adding new advanced state-of-the-art instrumentation. We will report about the experiment performed in June 2017 aiming at the A ∼ 80 region, where the BRIKEN neutron counter [10] was combined with the AIDA implant and decay detector [9]. Some preliminary results for T 1/2 and P n values will be presented and compared with theoretical calculations. Their impact on calculated abundances will be explored.
References
[1] C. Sneden et al., Ann. Rev. Astron. Astroph. 46, 24 (2008).
[2] C.J. Hansen et al., Astroph. J. 797, 123 (2014).
[3] R. Surman et al., AIP Advances 4, 041008 (2014).
[4] S. Wanajo, Astroph. J. Lett. 770, L22 (213).
[5] A. Perego et al., Month. Not. Roy. Astron. Soc. 443, 3134 (2014)
[6] T. Shafer et al., Phys. Rev. C 893, 055802 (2016).
[7] H. Okunoet al., Prog. Theor. Exp. Phys. 2012, 03C002 (2012).
[8] T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003 (2012).
[9] T. Davinson et al., http://www2.ph.ed.ac.uk/ td/AIDA/
[10] A. Tarifeo-Saldivia et al., J. Instrum. 12, 04006 (2017).
Primary author
Alvaro Tolosa Delgado
(IFIC (Instituto de Fisica Corpuscular))
