In order to accurately measure the cross-section of the 13C(n,n)16O reaction at stellar energies in the China JinPing underground Laboratory, a research team from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS) and their collaborators from Sichuan University and the Chinese Institute of Atomic Energy recently developed a high-efficiency low-background neutron detector array (CJPL).
Nuclear Science and Techniques published the study.
Important processes for the production and development of the elements include the slow neutron capture process (s-process) and the intermediate process (i-process). The s-process is used to create over half of the elements heavier than iron. The primary neutron source for the s- and i-processes is 13C(n,n)16O.
At stellar energy, the cross section of this reaction is very small (10-14 Barn), which results in significant measurement error and makes it challenging to limit theoretical extrapolation.
The researchers created a detector array made up of 24 3He proportional counters to precisely quantify the cross section of the 13C(n,n)16O reaction. A polyethylene cube with a 7 percent borated polyethylene covering protecting it contained the counters.
The background of the detector array was then measured on the ground and underground, respectively. The neutron background observed at CJPL was 265 times lower than the ground measurement, at only 4.5 counts/h.
Using the 3 MV tandem accelerator at Sichuan University and Monte Carlo simulations, the researchers also estimated the detection effectiveness of the array for neutrons in the energy range of 0.1 MeV to 4.5 MeV.
Using the findings of this study as a foundation, future research might examine the production and evolution of the elements in the universe by measuring the direct cross-section of the main neutron source processes in stars.