Scattering of 14.5 MeV neutrons from lithium in an LiI(Eu) scintillator

An experimental study of the scattering of 14.5 MeV neutrons from lithium in an LiI(Eu) scintillator was made by means of coincidence technique to correlate the pulse height produced in the scintillator with the time of flight of the scattered neutrons. The angular distributions of both elastically scattered and inelastically scattered neutrons have been obtained. A comparison of the LiI scintillator response to recoiling lithium ions and electrons was made over the range from 0 to 4 MeV. It was found that the recoiling lithium ions produced only about 3/10 as much light as electrons of the same energy. The scintillation response was found to be very nearly linear over the entire energy range studied. The principal inelastic interaction observed in this experiment was 7Li(n,n')7Li*(4.63 MeV) → α + 13H. The angular distribution of the inelastically scattered neutrons suggests tat the first step in this reaction proceeds by a direct interaction mechanism as opposed to compound nucleus formation. The shape of the pulse height peak observed in coincidence with the inelastic neutrons indicates that the α-T breakup of 7Li* was nearly isotropic in the recoiling lithium CM system. Conservation of angular momentum and parity suggests a value of 1 = 3 for the relative orbital angular momentum quantum number of the decay products. This is consistent with isotropic breakup only if no strong polarization effects occurred in the LiI target