Direct neutron-multiplicity sorting with a flat-efficiency detector

Photoneutron Cross-section Measurements for $^{165}$Ho by the Direct Neutron-Multiplicity Sorting at NewSUBARU

“…The total efficiency is 38.0-35.7% over a neutron energy up to 5 MeV. Based on Monte Carlo (MC) statistical model calculations on 209 Bi provided by Kawano [3], we confirmed that the average energy of the emission spectra is below 2-3 MeV, thus more than 90% of the emission spectrum is in the flat efficiency energy range of the detector. We applied the analysis procedure on the simulated data and reproduced the input cross sections for the MC simulations with a < 1% uncertainty.…”

“…For the IAEA-CRP, a flat-efficiency neutron detector (FED) for (γ, xn) cross-section measurements was developed. The detector consists of 3 He counters arranged in three concentric rings embedded in a polyethylene moderator. Due to the fact that the efficiency of the detector is constant for the neutron energies up to several MeV, it is possible to determine the partial photoneutron reactions cross sections using direct neutron-multiplicity sorting technique.…”

“…A flat efficiency neutron detection array [3] has been developed recently. The detection is based on the conversion of neutrons into charged particles through the 3 He(n, p)t reaction.…”

“…Such type of a detector is mandatory for the DNM sorting technique applied to obtain absolute (γ, xn) reaction cross sections, as described in details in Ref. [3].…”

“…Significant discrepancies between the cross sections measured at the two facilities were observed that cannot be resolved in a systematic manner [1,2]. In order to solve this issue, a direct neutron multiplicity (DNM) sorting technique has been developed [3]. The DNM method is based on the constant neutron detection efficiency with no dependence on the energy of the neutrons.…”