Measurement of keV-neutron capture cross-sections and capture γ-ray spectra of 56Fe and 57Fe

Abstract

The neutron capture cross-sections and the capture γ-ray spectra of 56Fe and 57Fe have been measured in the neutron energy range from 10 to 90 keV. Pulsed keV-neutrons were produced from the 7Li( p, n) 7Be reaction by bombarding a lithium target with a 1.5-ns bunched proton beam from a 3 MV Pelletron accelerator. The incident neutron spectrum on the capture sample was measured using a time-of-flight method with a 6Li-glass detector. The capture γ-rays emitted from an iron or standard gold sample were detected with a large anti-Compton NaI(Tl) spectrometer. The capture yield of the iron or gold sample was obtained by applying a pulse-height weighting technique to the corresponding capture γ-ray pulse-height spectrum. The capture cross-sections of 56,57Fe were derived with errors less than 5% using the standard capture cross-sections of 197Au. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. The present results for the capture cross-sections were compared with the previous measurements and the evaluated values of ENDF/B-VII.0 and JENDL-3.3. The Maxwellian-averaged capture cross-sections of 56Fe and 57Fe at 30 keV are derived as 12.22 ± 2.06 mb and 44.48 ± 7.56 mb, respectively.