Particle discrimination and fast neutron response for a NaIL:Tl and a NaI:Tl scintillator detector

Responses of fast neutrons and gamma-rays for a Li co-doped NaIL:Tl (NaIL) and a general sodium iodide NaI:Tl (NaI) were investigated with a waveform digitizer. The rise time of the pulses from NaIL is shorter than for NaI, while the decay time is shorter. The particle discrimination ability using charge integration approach was studied for NaIL and NaI with moderated Am-Be neutrons and D–T​ reaction neutrons. The results show the excellent discrimination property of NaIL between thermal neutron and gamma event, while the Figure of Merit (FoM) is up to 3.89, the peak to valley ratio is greater than 1000:1. Meanwhile, it is sensitive to fast neutron and it has the ability to discriminate proton and alpha in some extent, while the FoM between neutron and gamma event is larger than 1.6. The discrimination FoM between fast neutron and gamma event is larger than 1 for NaI, while that between proton and alpha cannot be achieved. The overall discrimination capability of NaIL is slightly better than NaI. At last, the difference of response and waveform induced by the interaction of fast neutrons with NaIL and NaI are analyzed and discussed.