Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,γ)175Yb reaction by the cadmium ratio method

Abstract

The thermal-neutron cross-section and the resonance integral for the 174Yb(n,γ)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am–Be neutron sources. The gamma-ray spectra from the activated samples were measured with a calibrated n-type high-purity Ge detector. The experimental results were corrected for the correction factors calculated for thermal and epithermal neutron self-shielding effects, epithermal neutron spectrum shape and gamma-ray self attenuation. Thus, the thermal neutron cross-section for the 174Yb(n,γ)175Yb reaction is found to be 126.5±6.6b, relative to that of the 55Mn monitor. The resonance integral value for the 174Yb(n,γ)175Yb reaction is found to be 59.6±8.5b, at cadmium cut-off energy of a 0.55eV. Using the measured cadmium ratios of 55Mn and 174Yb, the result for resonance integral of the 174Yb(n,γ)175Yb reaction has also been obtained relative to the reference value of the 55Mn monitor. The present results for the 174Yb(n,γ)175Yb reaction agree well only with the recent experimental ones obtained by Kafala et al. [1] and De Corte and Simonits [2] within uncertainty limits. However, the previously reported experimental data for the thermal neutron cross-section for this reaction are distributed between 24 and 141b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30–69b.