Measurement of the Eu-nat(n, ?) cross section up to 500 keV at the CSNS Back-n facility, and the stellar( 151,153)Eu(n, ?) cross section at s-process temperatures

In nuclear astrophysics, the nuclides(151)Eu and Eu-153 are both in the path of the s-process, and their (n,gamma)cross sections are important input parameters for the calculation of the nuclear astrophysics network. According to the EXFOR database, the neutron capture cross section of natural europium in the resonance region has not been fully measured. The (n,gamma) cross section of( nat)Eu was measured using the time-of-flight (TOF) technique at the Back-n white neutron source facility of the China Spallation Neutron Source(CSNS) in the 1 eV-to 500 keV range. Four C(6)D(6 )liquid scintillator detectors and pulse height weighting techniques were used to measure prompt gamma rays and analyze the data. The results of the analysis were compared with the evaluated data of ENDF/B-VIII.0 and JENDL-5.0. It shows that there are some differences between the measurement results and different evaluated data libraries. The resonance parameters of Eu-151 and( 153)Eu were extracted in the 1 eV-150 eV region using the R-Matrix code SAMMY. The accurate Maxwellian-averaged capture cross section (MACS) is derived over the temperature range of the s-process nucleosynthesis model. The result shows that at kT=30 keV, the MACS value of Eu-151 is 3417 +/- 297 mb and the value of Eu-153 is 2718 +/- 237 mb.