Ponente
Descripción
(On behalf of S505-DESPEC experiment collaboration)
Our understanding of the production of the heavy elements in the Universe is still incomplete. In particular the contribution of the rapid neutron capture (r-) process to the observed stellar abundances around mass number A~195 (the 3rd r-process peak), which is linked to the effect of N=126 shell closure in the production path. Given the lack of nuclear data, astrophysical abundance calculations must rely on theoretical predictions, for the important parameters T1/ 2 (half-life) and Pn (neutron emission probability). Both parameters are extracted from theoretical beta-strength distributions, which depend on nuclear structure. However, large discrepancies exist among different theoretical models [Mor14,Cab16]. Our aim is to discern between models by comparing with measured beta-strengths. For this we will use Total Absorption Gamma-ray Spectroscopy (TAGS) which is the most effective method for obtaining beta-strength distributions across the entire decay energy window [Rub05].
With this purpose, an experiment was performed at the GSI/FAIR facility in June 2022. During the experiment, the decay of Au and Pt isotopes with N=125-27 were measured. These isotopes were produced by high-energy nuclear reactions using a beam of Pb on a Be target and selected and identified using the FRagment Separator (FRS) [Win08]. Ion implants and decay electrons were measured with the Advanced Implantation and Decay Array (AIDA) [Hal23], while isomeric and β-delayed γ-ray cascades were measured with the Decay Total Absorption Spectrometer (DTAS) [Gua18], both developed within the NUSTAR/DESPEC collaboration.
We succeeded in performing clean implanted-ion identification, minimizing the contamination of ionic charge states and reactions in the FRS. We obtained for each isotope beta-gated TAGS decay spectra by combining the information from the three systems. We did a preliminary analysis of half-life and beta intensity distribution. We will discuss the status of the analysis and the work remaining.
References
[Cab16] R. Caballero-Folch et al., Phys. Rev. Lett. 117, 012501 (2016)
[Mor14] A.I. Morales et al., Phys. Rev. Lett. 113, 022702 (2014).
[Rub05] B. Rubio et al., J. Phys. G 31, S1477 (2005).
[Gua18] V. Guadilla et al., Nucl. Instrum. Meth. Phys. Res. Sect. A 910, 79 (2018).
[Hal23] O. Hall et al., Nucl. Instrum. Meth. Phys. Res. Sect. A 1050, 168166 (2023)
[Win08] M. Winkler, et al., Nuclear Instruments and Methods in Physics Research Section B 266 (2008) 4183.
