Ponente
Descripción
The measurement of neutron capture cross sections provides important nuclear data for the study of astrophysical phenomena, such as the slow neutron capture (s-) process, one of the main mechanisms of nucleosynthesis for isotopes heavier than $^{56}$Fe, which operates in red-giant and massive stars.
Time-of-fight facilities, such as n_TOF, provide point-wise cross sections covering the full energy range of astrophysical interest, which are essential for the study of the s- process.
This facility is specially well equipped for the study neutron capture cross sections with three complementary experimental areas: EAR1 [1] for TOF measurements of high neutron energy resolution, EAR2 [2] for TOF measurements with high luminosity, and the new NEAR facility [3] which provides a very high neutron flux as a quasi-stellar beam for activation measurements.
This contribution focuses on a recent experimental campaign [4], at EAR2-n_TOF, where a high-sensitivity setup [5], was used to measure the $^{146}$Nd(n,γ) cross section. This cross section is of special interest since s-process stellar model calculations using the reference (n,g) rates (or Maxwellian Averaged Cross section, MACS) data, by Bao et al. [6], based on measurements by Wisshak [7], show discrepancies with precise observational data from pre-solar stardust SiC grains, [8,9,10]. These discrepancies are removed when using stellar model calculations with an enhancement of 15\% of the $^{146}$Nd capture cross section, being especially sensitive to the variation at stellar temperatures (kT = 8 keV).
This contribution details the experimental methodology and the preliminary capture yield of this recent campaign, which had the primary objective of analysing the resolved resonance region (RRR) of 146Nd up to 5 keV, for the first time based on TOF data.
An outlook into a complementary campaign on the activation of $^{146}$Nd(n,γ), yielding $^{147}$Nd with a suitable half-life (≈11d) to directly determine the MACS, will be included. This campaign will take place in two facilities, being one of the first measurements at NEAR, a new facility still under characterisation, and another in the well established kT= 25 keV stellar spectrum at HiSPANoS-CNA [11], which uses the 7Li(p,n) reaction. The activation measurements will allow cross-check the data from the TOF data in the keV range of interest for astrophysics.
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(11) M.A. Millán-Callado et al., Radiation Physics and Chemistry 217 (2024)
