Measurement of Continuous Energy Neutron Incident Neutron Production Double Differential Cross sections

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The neutron-production double-differential cross sections for neutron incidence up to 800 MeV were measured up to 800 MeV at Los Alamos Neutron Science Center (LANSCE). The incident neutrons have continuous energies as emitted neutron at the facility. The energy of emitted neutron was obtained by the deposition energy of recoil proton from the radiator. The energy of incident neutron was determined by the time-of-flight method and the emitted neutron energy.First, the two sizes of phoswich type recoil proton detectors consist of Nal(Tl) and plastic scintillator were constructed and tested by the continuous energy neutron generated from the spallation reaction by Ar beam and Pb target at National Institute for Radiological Science (NIRS). Next, the detectors were checked by mono energetic proton up to 500 MeV at High Energy Accelerator Research Organization (KEK), We obtained the characteristics of the detectors experimentally.Then we measured the neutron-incident neutron-production (n, xn) double-differential cross sections at LANSCE. The irradiated targets were an iron and a lead. The detection angles were 15, 30 and 90 degrees. It was difficult to discriminate the neutron events from the background ones for the smaller phoswich detectors. To increase the detection efficiency, the combination of organic scintillator and the time-of-flight method was adopted. The scheme made the discrimination much clear and was effective for lower energy emitted neutron below 100 MeV.The capability of the measurement of (n, xn) double-differential cross sections for the continuous incident energy neutron was shown in this study.