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Neutrons from a source are moderated by means of hydrogenous materials such as polyethylene (PE) or water to reduce the energy of fast neutrons and to increase the fluence rate of moderated neutrons. The rise-time and γ-ray pulse height spectrum from a PE moderated241Am-Be neutron-gamma (n-γ) mixed source were measured by using6Li-BC501 scintillation detector and pulse shape discriminator (PSD) system. The difference in rise-time between γ and neutron signals tumed out to be 18.5 ns for the6Li-BC501 (n-γ) spectrometer system. The figure of merit (FOM) for this separation was estimated to be 1.52, and this was compared with the published results. From this comparison, the6Li-BC501 system has much superior characteristics in (n-γ) separation to other detector systems. Two Compton edges at around 1.87 and 3.99 MeV which are produced by H(n,γ)D reaction and by the first excited state of12C* from Be(α, n)12C* reaction were also investigated. [ABSTRACT FROM AUTHOR]