Measurement of the ${}^{159}$Tb(n, ${\hat{I}}^3$) cross section at the CSNS Back-n facility

Abstract

The stellar (n, ${\hat{I}}^3$) cross section data for the mass numbers around A $\approx$ 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occur in the thermally pulsing asymptotic giant branch (TP--AGB). The new measurement of (n, ${\hat{I}}^3$) cross sections for ${}^{159}$Tb was performed using the C${}_6$D${}_6$ detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source (CSNS) with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels were reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) were derived from the measured ${}^{159}$Tb (n, ${\hat{I}}^3$) cross sections at $kT$ = 5 $\sim$ 100 keV and 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 overestimate the present MACS up to 40$\%$ and 20$\%$, respectively. A sensitive test of the s-process nucleosynthesis was also performed with the stellar evolution code MESA. Significant changes in abundances around A $\approx$ 160 were observed between the ENDF/B-VIII.0 and present measured rate of ${}^{159}$Tb(n, ${\hat{I}}^3$)${}^{160}$Tb in the MESA simulation.

13 pages, 7 figures