Neutron capture cross section of ¹⁶⁹Tm measured at the CSNS Back-n facility in the energy region from 30 to 300 keV *

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.