Study on the Growth and Scintillation Properties of CLLB Crystals

Cs2LiLaBr6:Ce (CLLB) scintillation detector has excellent energy resolution and high light output to gamma-rays, with excellent neutron/gamma-rays discrimination performance. Its applications are mainly limited to crystal growth with large size and high quality. In this paper, high performance CLLB was grown, encapsulated and tested. The vertical Bridgman method was employed to grow Cs2LiLaBr6:1%Ce crystals. By regulating the temperature, the maximum temperature gradient of the growth furnace was adjusted to the position of crystal precipitation. To avoid the non-uniform melting component area, the non-stoichiometric of raw materials increasing the excess of 100% LiBr were used. The crystals was developed successfully with 1 inch diameter, 5 cm length, and 4.32 g/mL density. Finally, the crystal was encapsulated and tested, with an energy resolution of 4.0% and relative (NaI) optical output of 1.14 to 0.662 MeV gamma-rays, and an absolute optical output of 47665 Photons/MeV to 0.511 MeV gamma-rays; The figure of merit (FOM) of the neutron/gamma-rays discrimination is 1.27 enabled by charge comparison method. The scintillation decay time of the two kinds of signals is measured respectively by the optical flux simulation method, with a fast component of about 0.19 μs and a slow component of 1.08 μs. Results show that the neutron signals has a higher fast component proportion to gamma-rays signals.