Effects of 6LiF and 6LiCl codoping on gamma and neutron detection performance of NaI:Tl single crystal scintillators

NaI:Tl single crystals codoped with (LiI)-Li-6 have been considered as promising neutron-gamma scintillators due to low cost, scalability, and high efficiency in detecting and discriminating neutrons and gamma-rays. This study aims to study the effects of (LiF)-Li-6 and (LiCl)-Li-6 codoping on the NaI:Tl single crystals grown by the multi-ampoule Bridgman method. The impact of (LiF)-Li-6 and (LiCl)-Li-6 on the optical properties, gamma spectroscopy, and pulse shape discrimination (PSD) of neutron and gamma detection performance were analyzed. Both (LiF)-Li-6 and (LiCl)-Li-6 caused a decrease in gamma-ray light yield and a deterioratrion of energy resolution with increasing codoping concentrations, similar to the scenarios of (LiI)-Li-6 codoping. Nonetheless, for NaI:Tl,(LiF)-Li-6, the light yield and PSD Figure-of-Merit (FoM) are almost unchanged about 37,500 photons/MeV and 4.6 when the Li content reaches 2 at%, which is better than the scenario of (LiI)-Li-6 codoping. Combing with the advantages of non-hygroscopic nature of LiF and a higher utilization yield of Li element in LiF comparing with LiI, NaI:Tl,(LiF)-Li-6 single crystals could be regarded as more cost-effective scintillators for neutron detection applications.