Novel scintillation material Cs2LiLaBr6−xClx:Ce for gamma-ray and neutron spectroscopy

A new scintillation material CS₂LiLaBr_6-xCI_x:Ce (CLLBC:Ce) belonging to the elpasolite crystal family has been discovered and investigated at RMD. A Cs₂LiLaBr_4.8Cl_1.2: 2% Ce crystal was grown using the melt-based, vertical Bridgman method. The first grown crystal of CLLBC:Ce is 1.5 cm in diameter and a few inches in length. This material has a cubic structure, therefore, potentially can be grown in large sizes. Its scintillation properties have been studied under gamma and neutron irradiation. The presence of ⁶Li and ³⁵Cl in CLLBC:Ce allows for thermal and fast neutron detection, respectively. CLLBC´s response to fast neutrons via ³⁵Cl(n,p)³⁵S reaction was tested at different energies of mono-energetic fast neutron beam, acquired at the University of Massachusetts Lowell 5.5 MV Van de Graaff generator. A fast neutron peak was identified, and its centroid was observed to move linearly with the beam energy. The differences in the decay times of neutrons and gammas allowed pulse shape discrimination to differentiate between the two types of radiation. The material also shows an excellent response to gamma-ray irradiation, with gamma-ray energy resolution of ~3.0 % at 662 keV, and light output of 40,000 photons/MeV. These properties make CLLBC:Ce an excellent candidate for combined gamma-ray and neutron (thermal and fast) spectroscopy.