Tl-Doped CsI/⁶LiBr Scintillator for Thermal Neutron Detection With Ultrahigh Light Yield

In this study, a novel thermal neutron scintillator of Tl:CsI/LiBr was developed. The eutectics were fabricated at various growth rates and investigated their scintillation properties. As a material design guideline, Tl:CsI, which has an excellent
$\alpha /\gamma $
ratio, was selected as the scintillator phase to realize high light yield at the energy of
$\alpha $
-rays and tritons generated by the nuclear transmutation reaction with
⁶
Li and LiBr, which has a refractive index close to that of CsI, was selected as the neutron capture phase. Radioluminescence (RL) measurement under X-ray irradiation was also performed to obtain the emission spectrum of the eutectics. The light yield and decay time for thermal neutron were measured using
²⁵²
Cf and were much higher than those of conventional scintillators for thermal neutron. Furthermore, fabricated eutectic can have the higher sensitivity to thermal neutron due to the high
⁶
Li concentration compared to conventional single-crystal scintillators. Therefore, we have succeeded in developing a promising scintillator material.