First Results of the 64Ni (n, γ) Cross Section Measurement at nTOF

The neutron capture cross section of 64Ni is an important parameter in nuclear astrophysics that is needed to accurately simulate stellar nucleosynthesis and validate stellar models. 64Ni is among the seeds of the s-process and its capture cross section has been found to have an important effect on the predicted abundances of many nuclei synthesized in Asymptotic Giant Branch (AGB) and massive stars. Despite its relevance, the measurements of the 64Ni (n, γ) available in the literature are scarce and discrepant. For this reason, a new accurate time-of-flight measurement has been performed at the nTOF facility at CERN, taking advantage of its high instantaneous neutron flux, and using a highly enriched 64Ni sample. The first preliminary results show important discrepancies with respect to the cross sections recommended in the most recent releases of the evaluated nuclear data libraries. In particular, a large resonance reported at 9. 52 keV is not observed. As a consequence, a significant reduction in the Maxwellian-Averaged Cross Section (MACS) obtained from evaluated data libraries in the 5–25 keV thermal energy region is expected.