Development of a quasi-monoenergetic neutron field using the 7Li(p, n)7Be reaction in the 70–210 MeV energy range at RIKEN

A quasi-monoenergetic neutron field was developed using the 7Li(p, n)7Be reaction in the energy range from 70 to 210 MeV in the ring cyclotron facility at RIKEN. Neutrons were generated from a 10-mm-thick 7Li target injected by protons accelerated to 70, 80, 90, 100, 110, 120, 135, 150, 210 MeV. The neutron energy spectra were measured with an NE213 organic liquid scintillator using the TOF method. The absolute peak neutron yields were obtained by measurements of 478 keV γ-rays from 7Be nuclei produced in a 7Li target through the 7Li(p, n)7Be (g.s.+0.429 MeV) reaction. Two relative neutron fluence monitors, which were calibrated to the absolute peak neutron fluences by the 7Be measurement, were equipped along the neutron beam line during an irradiation experiment. This high-energy neutron field is very useful for neutron cross-section measurements, response measurements of neutron detectors, and shielding experiments.