Measurement of Pb 208 (n,γ) Pb 209 Maxwellian averaged neutron capture cross section

The doubly magic Pb208 nucleus is a bottleneck at the termination of the s-process path due to its very low neutron capture cross section. This cross section is also important for the decomposition of s, r processes and U/Th radiogenic decay contributions to the Pb-Bi solar abundances. The Pb208(n,γ)Pb209 cross section was measured at the Soreq Applied Research Accelerator Facility Phase I using an intense quasi-Maxwellian neutron source produced by irradiation of the liquid-lithium target with a 1.5-mA continuous-wave proton beam at 1.94 MeV. The cross section was measured by counting the β activity from the irradiated lead target. The measurement allowed us to evaluate the Maxwellian averaged cross section (MACS) at 30 keV obtaining a value of 0.33(2) mb. This has been compared with the earlier activation and time-of-flight measurements found in the literature. The MACS cross-sectional value of the Cu63(n,γ)Cu64 reaction was determined in the same experiment and is compared to a recent published value.