| C. Domingo-Pardo et al. (G. Aerts, S. Andriamonje, E. Berthoumieux, C. Carrapico, W. Dridi, F. Gunsing, C. Lampoudis, J. Pancin, L. Perrot, A. Plukis) |
The (n,g) cross section of 206 Pb has been measured at the CERN n TOF facility with high resolution in
the energy range from 1 eV to 620 keV by using two optimized C6 D6 detectors. In the investigated energy
interval about 130 resonances could be observed, from which 61 had enough statistics to be reliably analyzed
via the R-matrix analysis code SAMMY. Experimental uncertainties were minimized, in particular with respect to
(i) angular distribution effects of the prompt capture γ -rays, and to (ii) the TOF-dependent background due to
sample-scattered neutrons. Other background components were addressed by background measurements with an
enriched 208 Pb sample. The effect of the lower energy cutoff in the pulse height spectra of the C6 D6 detectors was
carefully corrected via Monte Carlo simulations. Compared to previous 206 Pb values, the Maxwellian averaged
capture cross sections derived from these data are about 20% and 9% lower at thermal energies of 5 keV and
30 keV, respectively. These new results have a direct impact on the s -process abundance of 206 Pb, which represents
an important test for the interpretation of the cosmic clock based on the decay of 238 U.
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