KENS keV neutron flux for nuclear astrophysics

A fast (keV) neutron is a unique probe for studying important problems on nuclear astrophysics as well as on nuclear physics, and the neutron is produced by several reactions such as nucleon exchange reaction, photo-nuclear reaction, and spallation reaction. Among the neutrons produced by these reactions the spallation neutron has characteristic features such as a white energy spectrum and a well collimated beam. In this study, the neutron flux of the spallation neutron source (KENS) was measured from thermal energy to 90 keV: the flux at 30 keV is about 12 n/(cm2 s eV) at a sample position 7.34 m from the water moderator for the proton beam current of 5 μA, comparable to the flux obtained by the 7Li(p, n)7Be reaction for the proton beam current of 10 μA at a sample position 12 cm from the 7Li target. The measured flux was compared to a calculated one using a Monte-Carlo code.