New Measurement of the Capture Cross Section of Bismuth and Lead Isotopes

All the stable lead isotopes and 209Bi have been recently measured at n_TOF [1] (CERN) in the range from 1 eV up to 1 MeV, using an optimized experimental setup. A set of two homemade C6D6 detectors with carbon-fibre canning was designed to greatly reduce the sensitivity to scattered neutrons. Surrounding elements like the sample holder and the sample exchanger have been made also of carbon fibre. The pulse-height weighting technique has been used in order to determine the (n,γ ) cross sections. Concerning this technique, special care has been taken in the treatment of several sources of error leading to a total systematic uncertainty of less than 3%. Results on the analysed 209Bi and 207Pb capture data and a comparison with previous experiments and evaluations are presented.