Measurement of the 159Tb(n, ?) cross section at the CSNS Back-n facility

The stellar (n, gamma) cross section data for the mass numbers around A approximate to 160 are of key importance to nucle-osynthesis in the main component of the slow neutron capture process, which occurs in the thermally pulsing asymptotic giant branch (TP-AGB). The new measurement of (n, gamma) cross sections for 159Tb was performed using the C6D6 detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels are reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) are derived from the measured 159Tb(n, gamma) cross sections at kT = 5-100 keV , are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 significantly over-estimate the present MACS up to 40% and 20%, respectively. A sensitive test of the s-process nucleosynthesis is also performed with the stellar evolution code MESA. Significant changes in abundances around A approximate to 160 are observed between the ENDF/B-VIII.0 and present measured rate of 159Tb(n, gamma) 160Tb in the MESA simulation.

Automated summary

The (n, gamma) cross section data for 159Tb was measured using the C6D6 detector system at the China spallation neutron source. The derived Maxwellian-averaged cross sections (MACS), based on the measured data, are in good agreement with KADoNiS-v0.3 and JEFF-3.3, but over-estimate significantly in KADoNiS-v1.0 and ENDF-VIII.0. The stellar evolution simulation using the obtained rate of 159Tb(n, gamma) 160Tb shows significant changes in abundances around A approximate to 160 compared to ENDF/B-VIII.0.