Akademik Veri Yönetim Sistemi
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, cilt.266, sa.11, ss.2549-2555, 2008 (SCI-Expanded)
The thermal-neutron cross-section and the resonance integral for the Yb-174(n,gamma)Yb-175 reaction were measured by the I activation method using a Mn-55 monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three Am-241-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 Yb-174(n,gamma) Yb-175 reaction is found to be 126.5 +/- 6.6 b, relative to that of the Mn-55 monitor. The resonance integral value for the Yb-174(n,gamma)Yb-175 reaction is found to be 59.6 +/- 8.5 b, at cadmium cut-off energy of a 0.55 eV. Using the measured cadmium ratios of Mn-55 and Yb-174, the result for resonance integral of the Yb-174(n, gamma)Yb-175 reaction has also been obtained relative to the reference value of the Mn-55 monitor. The present results for the Yb-174(n,gamma)Yb-175 reaction agree well only with the recent experimental ones obtained by Kafala et at. [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 141 b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30-69 b. (C) 2008 Elsevier B.V. All rights reserved.