Crystal growth, optical properties, and α-ray responses of Ce-doped LiCaAlF₆ for different Ce concentration

Ce 1%, 2%, and 3%-doped LiCaAlF₆ (LiCAF) single crystals were grown by the micro-pulling-down method. The crystals were transparent, 2.0 mm in diameter and 30-60 mm in length. Neither visible inclusions nor cracks were observed. Optical properties, including absorption coefficient, and photoluminescence emission spectra were measured. The strong absorption line was observed at 260 nm, and absorption coefficients of this line were proportional to Ce³⁺ concentration. Emission due to Ce³⁺ 5d-4f transition peaking around 285 nm and 310 nm were observed by 260 nm excitation. Simulating a neutron irradiation, ²⁴¹Am 5.5 MeV α-ray was used to excite the samples. After a correction of a quantum efficiency of photomultiplier tube and compared with Li-glass scintillator GS20, light yield of 6600 ph/n, and 41 ns decay were achieved 3% doped.