GAMMA-RAY PULSE-HEIGHT SPECTRUM OF AM-241-BE SOURCE BY LI-6-BC501 (N-GAMMA) SPECTROMETER SYSTEM

Neutrons from a source are moderated by means of hydrogeneous material s such as polyethylene (PE) or water to reduce the energy of hat neutr ons and to increase the fluence rate of moderated neutrons. The rise-t ime and gamma-ray pulse height spectrum from a PE moderated Am-241-Be neutron-gamma (n-gamma) mixed source were measured by using Li-6-BC501 scintillation detector and pulse shape discriminator (PSD) system. Th e difference in rise-time between gamma and neutron signals turned out to be 18.5 ns for the Li-6-BC501 (n-gamma) spectrometer system. The f igure of merit (FOM) for this separation was estimated to be 1.52, and this was compared with the published results. From this comparison, t he Li-6-BC501 system has much superior characteristics in (n-gamma) se paration to other detector systems. Two Compton edges at around 1.87 a nd 3.99 MeV which are produced by H(n,gamma)D reaction and by the firs t excited state of C-12 from Be(alpha,n)C-12* reaction were also inve stigated.