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

A quasi-monoenergetic neutron field was developed using the Li-7(p, n)Be-7 reaction in the energy range from 70 to 210 MeV in the ring cyclotron facil ity at RIKEN. Neutrons were generated from a 10-mm-thick Li-7 target inject ed 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 scint illator using the TOF method. The absolute peak neutron yields were obtaine d by measurements of 478 keV gamma-rays from Be-7 nuclei produced in a Li-7 target through the Li-7(p, n)Be-7 (g.s. + 0.429 MeV) reaction. Two relativ e neutron fluence monitors, which were calibrated to the absolute peak neut ron fluences by the 7Be measurement, were equipped along the neutron beam l ine during an irradiation experiment. This high-energy neutron field is ver y useful for neutron cross-section measurements, response measurements of n eutron detectors, and shielding experiments. (C) 1999 Elsevier Science B.V. All rights reserved.