Measurement of the neutron capture cross section of the s -only isotope 204 Pb from 1 eV to 440 keV

Abstract

The neutron capture cross section of 204Pb has been measured at the CERN n TOF installation with high resolution in the energy range from 1 eV to 440 keV. An R-matrix analysis of the resolved resonance region, between 1 eV and 100 keV, was carried out using the SAMMY code. In the interval between 100 keV and 440 keV we report the average capture cross section. The background in the entire neutron energy range wasreliably determined from the measurement of a 208Pb sample. Other systematic effects in this measurement were investigated and precisely corrected by means of detailed Monte Carlo simulations. We obtain a Maxwellian average capture cross section for 204 Pb at kT=30 keV of 79(3) mb, in agreement with previous experiments. However our cross section at kT=5 keV is about 35% larger than the values reported so far. The implications of the new cross section for the s-process abundance contributions in the Pb/Bi region are discussed.