Measurement and analysis of $^{155,157}$Gd(n,$\gamma$) from thermal energy to 1 keV

We have measured the capture cross section of the $^{155}$Gd and $^{157}$Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C$_{6}$D$_{6}$ detectors, and the capture yield was deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR.