Measurement of thermal neutron cross section and resonance integral for 165Ho(n, γ)166gHo reaction by the activation method

The thermal neutron cross section and the resonance integral of the reaction 165Ho(n, γ)166gHo were measured by the activation method using 55Mn(n,γ)56Mn monitor reaction. The sufficiently diluted MnO2 and Ho2O3 samples with and without a cylindrical Cd case were irradiated in an isotropic neutron field of the 241Am-Be neutron sources. The γ-ray spectra from the irradiated samples were measured with a calibrated n-type high purity Ge detector. Thus, the thermal neutron cross section for 165Ho(n,γ)166gHo reaction has been determined to be 59.2 ± 2.5 b relative to the reference thermal neutron cross section value of 13.3 ± 0.1 b for the 55Mn(n,γ)56Mn reaction, and it generally agrees with the recent measurements within about 1 to 12%. The resonance integral has also been measured relative to the reference value of 14.0 ± 0.3 b for the 55Mn(n,γ)56Mn reaction using an epithermal neutron spectrum of the 241Am-Be neutron source. The resonance integral for 165Ho(n, γ)166gHo reaction obtained was 667 ± 46 b at a cut-off energy of 0.55 eV for 1 mm Cd thickness. The existing experimental and evaluated data for the resonance integral are distributed from 618 to 752 b. The present resonance integral value agrees with most of the previously reported values obtained by 197Au standard monitor within the limits of error.