Measurement of the Ru(n,γ) cross section up to 700 keV at CSNS Back-n and constraint of stellar cross section of ruthenium isotope

摘要: The neutron capture cross sections of ruthenium play a crucial role in the stellar nucleosynthesis of nuclear astrophysics, the tracer element analysis of terrestrial and extraterrestrial samples, and the nuclear forensics and reactor monitoring. However, its (n,γ) cross sections haven’t be measured very precisely. The neutron capture cross section of ruthenium was measured by the time-of-flight(TOF) method from 1 eV to 700 keV at the back-n facility of the Chinese Spallation Neutron Source. The prompt γ rays emitted by de-excitation of compound neuclei were recorded by the C6D6 detectors. Yield and cross section data of neutron capture were obtained after thoughtful corrections and processing to the raw data. In the resolved resonance energy region from 1 eV to 1000 eV, some discrepancies were observed, offering valuable insights into the differences between four prominent evaluated data libraries. And the resonance parameters are extracted using Multilevel R-matrix Bayesian code SAMMY. In the unresolved energy region the average cross sections were obtained for the first time from 10 keV to 700 keV, which strongly constrain the neutron capture cross section of each ruthenium isotope. The TALYS code is applied to derive the averaged cross sections of nature ruthenium and each isotopes. Then the stellar Maxwellian average cross section was calculated from kT = 5 to 100 keV over a sufficiently wide range of neutron energies of s-process. Further experimental measurements of some important isotope of ruthenium such as 99Ru are strongly suggested.