Credit: Nuclear Science and Techniques
Photograph of the C6D6 detector system in the Back-n facility of the CSNS. A natural carbon sample is placed in the aluminum sample holder.
For decades, scientists have been on a quest to unravel the mysteries behind the creation of elements heavier than iron. At the heart of this exploration lie two primary neutron capture processes: the s(slow) and r(rapid) processes. Both of these play a crucial role in shaping the solar abundances we observe. Delving into the intricacies of the s-process since the 1950s, researchers have uncovered that it is not a singular process. Instead, to account for the solar abundances, it's divided into at least two distinct pathways: the main and the weak s-processes. These pathways are associated with specific stellar phenomena, notably the inner shell of the thermally pulsing asymptotic giant branch (AGB) stars, and during convective core He burning and subsequently during convective carbon shell burning in massive stars. The unique contributions of each s-process add layers of complexity to our comprehension of elemental formation. To deepen our understanding, it's imperative to obtain trustworthy data from nuclear experiments, especially those utilizing lanthanum bromide detectors crucial for neutron and γ-ray detector design and optimization.
A study in nuclear astrophysics is published in the journal of Nuclear Science and Techniques, researchers from Sun Yat-sen University, have made a significant contribution in this area with their novel study on neutron capture by bromine, conducted at the China Spallation Neutron Source and provides invaluable insights into both astrophysics and cutting-edge detector design.
At the China Spallation Neutron Source's Back-n facility, researchers harnessed four specialized C6D6 detectors to observe prompt γ-rays from neutron-induced capture events. Leveraging advanced data analysis techniques, such as the pulse-height weighting and double bunch unfolding methods based on Bayesian theory, they ensured meticulous background deductions, normalization, and corrections. The SAMMY code, a multilevel R-matrix Bayesian tool, was central to analyzing the capture yields in the observed energy spectrum, enabling the extraction of resonance parameters. While their results aligned with prior studies, notable discrepancies with certain databases emerged. The TALYS code, grounded in the Hauser–Feshbach statistical emission model, was vital in describing average cross-sections in unresolved resonance regions. The study's pinnacle was calculating the Maxwell average cross sections (MACSs) for bromine isotopes and contrasting them with extant databases and recommended values. Through a combination of precision and advanced methodologies, the team not only deepened the comprehension of neutron capture by bromine but also illuminated broader implications for astrophysics and detector design.
Moreover, these findings are set to shape the design and enhancement of upcoming neutron and γ-ray detectors, advancing the boundaries of nuclear experimentation. This study lays a solid foundation for subsequent investigations, poised to uncover more cosmic mysteries.
More information
Yang, GL., An, ZD., Jiang, W. et al. Measurement of Br(n,γ) cross sections up to stellar s-process temperatures at the CSNS Back-n. NUCL SCI TECH 34, 180 (2023). https://doi.org/10.1007/s41365-023-01337-6
Funding information
The National Natural Science Foundation of China (U1832182, 11875328, 11761161001, and U2032137)
The Natural Science Foundation of Guangdong Province, China (18zxxt65 and 2022A1515011184)
The Science and Technology Development Fund, Macau SAR (008/2017/AFJ)
The Macao Young Scholars Program of China (AM201907)
The China Postdoctoral Science Foundation (2016LH0045 and 2017M621573)
The Fundamental Research Funds for the Central Universities (22qntd3101 and 2021qntd28)
