Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the Reaction 127I(n, γ)128I

Abstract

The thermal neutron (2,200 m/s neutron) capture cross section (σ0) and the resonance integral (I 0) of the reaction 127I(n, γ)128I were obtained. The targets of the iodine were irradiated within and without a cadmium capsule at Rikkyo University Research Reactor. Characteristic features of neutron field were monitored by Co/Al and Au/Al wires. Gamma-rays from the irradiated targets were measured by a high purity Ge detector. The γ-ray spectra were taken successively and the decay of peak-area counts of the 443 keV γ-ray of 128I was followed. A half-life of 128I obtained was 24.72±0.03 min. The σ0 and I 0 of the reaction 127I(n, γ)128I were deduced from the analysis of obtained γ-ray spectra according to the Westcott's convention and were 6.40±0.29 barns and 162±8 barns, respectively. The previous measurements of the σ0 and I 0 of the reaction 127I(n, γ)128I were reviewed and differences between the present values and the previous results were discussed with special emphasis on the experimental results by Friedmann et al., whose experiment was the same as the present simultaneous measurement of the σ0 and I 0.