Neutron capture cross section of 169Tm measured at the CSNS Back-n facility in the energy region from 30 to 300 keV * *Supported by the National Natural Science Foundation of China (11790321, 11805282) and the National Key Research and Development Program of China (2016YFA0401601)

Abstract

The capture cross sections of the 169Tm reaction were measured at the back streaming white neutron beam line (Back-n) of the China Spallation Neutron Source (CSNS) using four C6D6 liquid scintillation detectors. The background subtraction, normalization, and correction were carefully considered in the data analysis to obtain accurate cross sections. For the resonance at 3.9 eV, the R-matrix code SAMMY was used to determine the resonance parameters with the internal normalization method. The average capture cross sections of 169Tm for energy between 30 and 300 keV were extracted relative to the 197Au reaction. The measured cross sections of the 169Tm reaction were reported in logarithmically equidistant energy bins with 20 bins per energy decade with a total uncertainty of 5.4% – 7.0% in this study and described in terms of average resonance parameters using a Hauser-Feshbach calculation with fluctuations. The point-wise cross sections and the average resonance parameters showed fair agreement with the evaluated values of the ENDF/B-VIII.0 library in the energy region studied.