Speaker
Description
David Rodríguez García on behalf of DESPEC collaboration
Our understanding of the production of the heaviest elements in the Universe is still incomplete. In particular the contribution of the rapid neutron capture (r-) process to the observed abundances of elements with A>180 and the astrophysical site for this process is uncertain. Combining astronomical observations (including gravitational wave detection), nuclear physics laboratory experiments and theoretical modelling we can advance in the solution of the puzzle.
Obtaining nuclear data, particularly in the heavy mass region around A~195 (the 3rd peak), is challenging due to limited experimental data availability. This region is linked to the N=126 shell closure in the production path. Consequently, reliance on theoretical predictions is necessary, especially for vital parameters like T1/2 (half-life) and Pn (neutron emission probability), derived from beta-strength calculations dependent on nuclear structure. However, discrepancies exist in theoretical calculations, particularly near N=126 [Mor14,Cab16], leading to a need for comparison with experimental data. Total Absorption Gamma-ray Spectroscopy (TAGS) proves the most effective method for obtaining beta-strength distributions across the entire energy spectrum [Rub05].
In June 2022, a experiment was performed at the GSI facility, as part of FAIR Phase-0, using the TAGS technique. During the experiment, isotopes of Hg, Au and Pt with N=125-27 were measured. These isotopes were produced by high-energy nuclear reactions with a beam of Pb on Be and selected and identified using the FRagment Separator (FRS) [Win08]. Ion implantations and decays particles were measured with the Advanced Implantation and Decay Array (AIDA) [Hal23], while isometic and β-delayed γ-ray cascades were measured with the Decay Total Absorption Spectrometer (DTAS) [Gua18], both developed within the NUSTAR/DESPEC collaboration.
The analysis of the data is ongoing. Currently, we are working on several fronts. One is the calibration of the FRS detectors in order to improve the identification (A and Z) of the nuclei implanted in AIDA.
We are also analysing DTAS data obtained from the measurement of several radioactive sources and comparing the results with detailed Monte Carlo simulations to benchmark the calculated spectrometer response. And finally we are working on AIDA calibration and noise reduction to be able to construct implant-beta correlations to select the proper gamma decay data. In the talk I will give examples of these.
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.
