Stellar neutron capture cross sections of Pr and Dy isotopes

The neutron capture cross sections of 160Dy, 161Dy, 162Dy, 163Dy, 164Dy, and 141Pr have been measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7Li(p,n)7Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π barium fluoride detector. The cross sections were determined relative to the gold standard. For the first time the correction for undetected capture events was completely obtained from experimental information, using capture cascades derived from measurements with an ADC system. The cross section ratios could be determined with an overall uncertainty of 1-1.5%, an average improvement compared to previous measurements by a factor 4. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=10 keV and 100 keV. For most of the isotopes there is reasonable agreement with recent evaluations, but discrepancies of ∝20% were obtained for 160Dy and 164Dy. (orig.)