Investigation of the phase diagram of the CsI-LiBr system and fabrication of the eutectic scintillator for thermal neutron detection

3He gas detectors have been commonly used in applied technology related to thermal neutron detectors; however, owing to the depletion of 3He, applications using solid-state scintillators are expanding. In recent years, our group has reported a novel Tl:CsI/6LiBr eutectic scintillator for thermal neutron detection, which has excellent light yield and (n,gamma) discrimination ability. In practical applications of eutectic scintillators, achieving eutectic production precisely at the eutectic point is crucial to ensure a high production yield and the development of a uniform eutectic structure. However, the phase diagram of the CsI-LiBr system has not yet been reported. In this study, the phase diagram obtained from calorimetry was investigated. Furthermore, eutectic fabrication was performed at the eutectic point, and the neutron response was evaluated.