Recently, researchers from the Institute of Modern Physics of the Chinese Academy of Sciences, Sichuan University and the China Institute of Atomic Energy Sciences have developed a high-efficiency and low-background neutron detection array, which provides a high-performance detector system for the accurate measurement of stellar neutron source reaction 13C (α, n) 16O in Jinping Deep Ground Laboratory. The results were published as cover articles in Nuclear Science and Techniques.
The slow neutron capture process (s-process) and the intermediate neutron capture process (i-process) are important processes in the origin of elements in the universe. Of these, the s-process contributes about half of the elements in the nucleosynthesis of superferro. The 13C(α,n)16O reaction is a neutron source reaction of s-process versus i-process. Due to the extremely low cross-section of the reaction (in the order of 10-14 targets), the experimental data error of the reaction near the astrophysical energy region is large, and it is difficult to effectively test and constrain the theoretical extrapolation results.
Figure 1: Detection efficiency varies with energy
Figure 2:Detection efficiency scale using a 3MV accelerator of Sichuan University and background measurement in Jinping Deep Ground Laboratory (Nuclear Science and Techniques cover)
In order to accurately measure the 13C (α,n)16O reaction cross-section, the researchers designed a set of high-efficiency low-background neutron detection array composed of 24 helium-3 proportional tubes, and carried out neutron background measurements of the detection array in Jinping Deep ground laboratory, and measured that the background level was 265 times lower than that of the ground.
The efficiency scale and simulation of neutron detection arrays are the main factors affecting the systematic error of neutron source reaction experiments. The researchers used the 3MV tandem accelerator of Sichuan University to scale the detection efficiency of the array, and combined with THE GEONT4 software simulation, the detection efficiency of the detection array on the 2.5 MeV neutron was 26%. In addition, the researchers also quantitatively studied the effect of angular distribution on detection efficiency. Studies have shown that this detection system can meet the measurement requirements of neutron source reaction 13C (α,n)16O. The research work has laid the foundation for the experimental study of neutron source reactions in the deep ground.
The research work is supported by major projects of the National Natural Science Foundation of China and the Youth Fund.
Related paper information:https://doi.org/10.1007/s41365-022-01030-0
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