Speaker
Description
To understand the processes leading to the formation of heavy elements in stars, it is essential to have detailed knowledge of neutron-induced cross-sections [1]. In the context of rapid neutron capture (r-process), direct measurement of these cross-sections is often impractical due to the short lifetimes and high radioactivity of the relevant nuclei. A common method to address these challenges is the use of surrogate reactions. In this approach, the compound nucleus of interest is produced through an alternative, experimentally accessible reaction [2]. However, using this method in direct kinematics presents challenges, such as significant background noise, low efficiency and difficulties in detecting low-energy neutrons.
To address these issues, we proposed the NECTAR (NuclEar reaCTions At storage Rings) project [3], which aims to measure different decay probabilities using inverse kinematics in a heavy-ion storage ring. This approach offers the significant advantage of directly detecting heavy fragments produced after the de-excitation of the compound nucleus, fragments that would otherwise be stopped in a target, instead of neutrons or gamma rays. The NECTAR project enables simultaneous measurement of gamma emission, neutron emission, and fission probability with unprecedented precision and efficiency.
In 2022, we conducted an experiment at the ESR storage ring at GSI/FAIR, during which we measured, for the first time, the neutron emission probability in the $^{208}$Pb($p,p’$) reaction [3], as well as the gamma emission probability [4], achieving a detection efficiency close to 100%. Following this successful experiment, the experimental setup was upgraded with the fission detectors, preparing it for the next experiment in 2024. This time, we used a beam of $^{238}$U and a deuteron target, enabling the simultaneous investigation of two excited nuclei, $^{238}$U and $^{238}$U produced in the $^{238}$U($d,d’$) $^{238}$U($d,p$) reactions respectively. We measured not only the gamma and neutron emission probabilities but also the probabilities for the emission of two and three neutrons, as well as the fission probability. This comprehensive approach allowed for the measurement of all possible decay channels within this excitation energy range in a single experiment with unprecedented detection efficiency. This contribution will discuss the methodological and technical advancements achieved under the NECTAR project and present the results obtained from the most recent experiment utilizing a uranium beam.
[1] M. Arnould and S. Goriely, Prog. Part. Nucl. Phys. \textbf{112}, (2020) 103766.
[2] R. Perez Sanchez et al., Phys. Rev. Lett. \textbf{125}, (2020) 122502
[3] https://www.lp2ib.in2p3.fr/nucleaire/nex/erc-nectar/
[4] M. Sguazzin et al., accepted in Phys. Rev. Lett. https://arxiv.org/abs/2312.13742
[5] M. Sguazzin et al., accepted in Phys. Rev. C https://arxiv.org/abs/2407.14350
To understand the processes leading to the formation of heavy elements in stars, it is essential to have detailed knowledge of neutron-induced cross-sections [1]. In the context of rapid neutron capture (r-process), direct measurement of these cross-sections is often impractical due to the short lifetimes and high radioactivity of the relevant nuclei. A common method to address these challenges is the use of surrogate reactions. In this approach, the compound nucleus of interest is produced through an alternative, experimentally accessible reaction [2]. However, using this method in direct kinematics presents challenges, such as significant background noise, low efficiency and difficulties in detecting low-energy neutrons.
To address these issues, we proposed the NECTAR (NuclEar reaCTions At storage Rings) project [3], which aims to measure different decay probabilities using inverse kinematics in a heavy-ion storage ring. This approach offers the significant advantage of directly detecting heavy fragments produced after the de-excitation of the compound nucleus, fragments that would otherwise be stopped in a target, instead of neutrons or gamma rays. The NECTAR project enables simultaneous measurement of gamma emission, neutron emission, and fission probability with unprecedented precision and efficiency.
In 2022, we conducted an experiment at the ESR storage ring at GSI/FAIR, during which we measured, for the first time, the neutron emission probability in the
Pb() reaction [3], as well as the gamma emission probability [4], achieving a detection efficiency close to 100%. Following this successful experiment, the experimental setup was upgraded with the fission detectors, preparing it for the next experiment in 2024. This time, we used a beam of U and a deuteron target, enabling the simultaneous investigation of two excited nuclei, U and U produced in the U() U(
) reactions respectively. We measured not only the gamma and neutron emission probabilities but also the probabilities for the emission of two and three neutrons, as well as the fission probability. This comprehensive approach allowed for the measurement of all possible decay channels within this excitation energy range in a single experiment with unprecedented detection efficiency. This contribution will discuss the methodological and technical advancements achieved under the NECTAR project and present the results obtained from the most recent experiment utilizing a uranium beam.
[1] M. Arnould and S. Goriely, Prog. Part. Nucl. Phys. \textbf{112}, (2020) 103766.
[2] R. Perez Sanchez et al., Phys. Rev. Lett. \textbf{125}, (2020) 122502
[3] https://www.lp2ib.in2p3.fr/nucleaire/nex/erc-nectar/
[4] M. Sguazzin et al., accepted in Phys. Rev. Lett. https://arxiv.org/abs/2312.13742
[5] M. Sguazzin et al., accepted in Phys. Rev. C https://arxiv.org/abs/2407.14350
| Consent | Yes |
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