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The 3He gas is commonly used for the detection of thermal neutrons. However, with the depletion of 3He gas, there is a need to develop new solid scintillators for thermal neutron detection. Solid scintillators containing 6Li, which have large neutron capture cross-sections and a large amount of energy released by transmutation reactions, are commonly used as alternative candidates. However, only single-crystal scintillators are currently used, and their 6Li concentration is limited by their chemical composition. In this study, we designed, grew, and evaluated a new eutectic scintillator, Rb2CeCl5/LiCl, which can improve the 6Li concentration compared with single-crystal scintillators. Rb2CeCl5, which was selected as the scintillator phase, has excellent scintillator properties (light yield: 36,000 photons/MeV, decay time: mostly 24 ns, slightly 153 ns), and is less deliquescent than other halide scintillators. The crystal grown using the vertical Bridgman method exhibited a eutectic phase composed of Rb2CeCl5 and LiCl. The eutectic crystals exhibited Ce3+ 5d-4f emissions, with a peak between 360 and 370 nm. The Rb2CeCl5 phase was identified as the luminescent phase via cathodoluminescence mapping, and 16,000 photons/neutron of the light yield and 56.1 ns of the decay time were observed. This study indicates that the Rb2CeCl5/LiCl eutectic scintillator is a promising candidate for use in thermal neutron detectors. [ABSTRACT FROM AUTHOR]

In recent years, thermal neutron detection using scintillators has been used in a wide range of fields. Thus, the development of scintillators with a higher light yield, faster decay, and higher sensitivity for thermal neutrons is required. In this study, K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were developed as novel eutectic scintillators for thermal neutron detection. LiCl was selected as the neutron capture phase and K2CeCl5 and CeCl3 were used as the scintillator phases. The eutectics of K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were prepared using the Vertical Bridgman method and the phases were identified by scanning electron microscopy and powder X-ray diffraction measurements. The results of radioluminescence measurements under Ag source X-ray tube irradiation confirmed that the 5d-4f emission derived from Ce3+. The cathodoluminescence spectra and thermal neutron responses of the prepared eutectics were measured to evaluate their optical properties. [ABSTRACT FROM AUTHOR]

The technology to grow single crystals of the required shape directly from a melt has been researched extensively and developed in various industries and research fields. In this study, a micro-pulling-down method and a Mo crucible were applied to the shape-controlled crystal growth of Y 3 Al 5 O 12 :Ce (YAG:Ce). Three types of Mo crucibles with different die shapes were developed. Stable crystal growth of more than 50 mm in length was achieved with the same shape as the die, and scintillation light output of ~20,000 ph/MeV, which is comparable with those of the YAG:Ce crystal grown by Cz method, were obtained. The transmittance of grown crystals above 500 nm was above 70%. The standard deviation (σ) of the scintillation light output at each position of the 50-mm-long sample was found to be within ±16%. [ABSTRACT FROM AUTHOR]