Accurate measurement of the I neutron capture cross-section in the keV neutron region

Rovira Leveroni, G.   ; Kimura, Atsushi   ; Nakamura, Shoji  ; Endo, Shunsuke   ; Iwamoto, Osamu  ; Iwamoto, Nobuyuki  ; Katabuchi, Tatsuya*

The I neutron capture cross-section was measured at the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline in the Materials and Life Science (MLF) facility of the Japan Proton Accelerator Research Complex (J-PARC). To obtain accurate results in the keV neutron region, the recently developed neutron filtering technique was employed with a 20-cm-thick Si filter to tailor the incident neutron flux into quasi-monoenergetic neutron peaks with averaged neutron energies of 51.5 and 127.7 keV and, at the same time, hugely increase the signal-to-noise ratio. The present cross-section results were determined form the capture yield ratio of I to that of Au and using the evaluated nuclear data from JENDL-5 as reference. The I neutron capture cross section was found to be 0.278 0.034 b at 51.5 keV and 0.141 0.015 b 127.7 keV, validating the JENDL-5 and JEFF-3.3 evaluations, as well as the results from Noguere et al., in contrast to the larger evaluations of JENDL-4.0 and ENDF/B-VIII.1 and the data from Macklin et al.