Measurement of Br(n,γ) cross sections up to stellar s-process temperatures at the CSNS Back-n

The neutron capture cross sections (n,gamma) of bromine were obtained using the time-of-flight technique at the Back-n facility of the China Spallation Neutron Source. Prompt gamma-rays originating from neutron-induced capture events were detected using four C6D6 detectors. The pulse-height weighting technique and double-bunch unfolding method based on Bayesian theory were used in the data analysis. Background deductions, normalization, and corrections were carefully considered to obtain reliable measurement results. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in the unresolved resonance region (URR) were obtained from 10 to 400 keV. The experimental results were compared with data from several evaluated libraries and previous experiments in the RRR and URR. The TALYS code was used to describe the average cross sections in the URR. The astrophysical Maxwell average cross sections (MACSs) of Br-79,Br-81 from kT = 5 to 100 keV were calculated over a sufficiently wide range of neutron energies. At a thermal energy of kT=30 keV, the MACS value for Br-79 682 +/- 68 mb was in good agreement with the KADoNiS v1.0 recommended value. By contrast, the value of 293 +/- 29 mb for Br-81 was substantially higher than that of the evaluated database and the KADoNiS v1.0 recommended value.

Automated summary

In this study, the neutron capture cross sections of bromine were obtained using the time-of-flight technique at the Back-n facility of the China Spallation Neutron Source. The average cross sections in different energy regions were calculated and compared with other data, and the astrophysical Maxwell average cross sections were also determined.