Neutron capture cross section measurements for Lu-nat with different thickness

The C6D6 detection system coupling with the pulse height weighting technique is widely used forexperimentally measuring the neutron capture cross section. The thickness of sample used in the experimentdirectly affects the neutron beam time and the reliability of the experimental data. In the present work, wecompare the lutetium (Lu) neutron capture reaction cross sections among the samles with different thickness,obtained by the C6D6 detection system of the back-streaming white neutron beam line at China spallationNeutron Source (CSNS back-n). The light response of the detection system is simulated with the considerationof the sample thickness by GEANT4 Monte Carlo simulation code. The 4th order polynomial pulse weightfunctions for different samples are determined by using the above light response function. In the experiment, thehigh precision capture yield distributions in the resonance energy region are obtained by measuring the longerflight distance and background. The experimental resonance parameters are deduced by analyzing the captureyield distribution with the R-matrix theory. The comparisons of the results of capture yield and the resonanceparameters between the two groups show that the resonance curve of 1.06mm natLu sample changes due to itsthickness effect, and there is a large difference between the experimental resonance parameters and ENDF/B-VIII.0 database. However, the experimental results of 0.207mm natLu sample can well accord with the ENDF/B-VIII. 0 data