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]. Recently, the more exotic i-process, which involves higher neutron densities and more exotic nuclei than the s-process [2], is also gaining great interest.
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 [3]. The situation has improved in recent years with the combination of facilities with high instantaneous flux, such as the n_TOF-EAR2 facility, with detection systems with an enhanced detection sensitivity and high counting rate capabilities [4,5,6]. In this context, this contribution will present a brief summary about recent improvements at the n_TOF facility and some highlights of TOF measurements of key isotopes.
Despite the significant progresses, the TOF technique is still not capable to adress the neutron capture cross section of many key unstable isotopes [3,7]. And for others, it did not suceed to provide data over the complete neutron-energy ranges in order to derive direct information of astrophysical interest [8,9,10]. In this context, complementing the TOF technique with activation measurements in a quasi-stellar beam, when feasible, may deliver complementary and more accurate information on a specific cross section [8]. Moreover, the unsurpassed sensitivity of activation measurement opens the door to first-time measurements on much smaller sample quantities [7]. Following this logic, n_TOF has recently deployed the new high-flux n_TOF-NEAR activation station [11]. An overview will be given on recent activities and plans at the NEAR facility, including the development of CYCLING, a cyclic ativation station for (n,g) measurements. Last, future perspectives for neutron capture measurements CERN will also be briefly discussed, such as the possibilities of the ultra high-luminosity BDF neutron source and the synergic cooperation with ISOLDE to produce unstable targets.
References
[1] F. Käppeler, et al., Reviews of Modern Physics 83, 157 (2011)
[2] J.J. Cowan, W.K. Rose, Astrophys. J. 212, 149–158 (1977)
[3]. Guerrero et al., The European Physical Journal A 53, 87 (2017)
[4] J. Lerendegui-Marco et al, Recent highlights and prospects on (n,g) measurements at the CERN n_TOF facility, arXiv:2310.15714 (2024)
[5] V. Alcayne et al., Rad. Phys. Chem. 217, 111525 (2024)
[6] J. Balibrea-Correa, Nucl. Inst. Meth. A 1064, 169385 (2024)
[7] Domingo-Pardo, C. et al., Eur. Phys. J. A 59, 8 (2023).
[8] C. Guerrero, et al., (n_TOF Collaboration), Phys. Rev. Lett. 125, 142701 (2020)
[9] J. Balibrea et al., EPJ Web of Conferences 279, 06004 (2023)
[10] J. Lerendegui-Marco et al., EPJ Web of Conferences 279, 06004 (2023)
[11] N. Patronis et al, The CERN n TOF NEAR station for astrophysics- and application-related neutron activation measurements, arXiv:2209.04443 (2023)
