Experimental Studies Related to s- and r- Process Abundances

The accurate determination of the neutron capture cross sections at stellar temperatures of kT=10-100 keV is an essential prerequisite for investigations of the nucleosynthesis of heavy elements. For this purpose a 4π Barium Fluoride Detector was constructed at Karlsruhe and implemented at the 3.75MV Van de Graaff accelerator. Over the last decade the cross sections of 57 isotopes have been measured in the mass range from Cd to Ta with typical uncertainties of 1-2%, an improvement up to factors 5-10 compared to other methods. These data were used in extensive s-process studies based on phenomenological and stellar models for deriving reliable sets of s- and r-process abundances.