Lithium Alkaline Halides—Next Generation of Dual Mode Scintillators.

We report on a new family of scintillators - Lithium alkaline halides, developed based on the alkaline halides by introducing lithium for dual mode gamma-neutron detection. Many different compositions were grown, among which LiSr2I5 (LSI), LiCa2I5 (LCI), LiSr2Br5 (LSB) activated with divalent Europium show good gamma and neutron detection properties. LSI shows the main emission at \sim 497 nm under X-ray excitation. It also shows good proportionality, which in combination with the light yield as high as 60000 photons/MeV, results in an energy resolution of 3.5% at 662 keV. The electron or gamma equivalent energy (GEE) of the thermal neutron peak due to the ^6Li neutron capture is 4.1 MeV, which amounts to a very high neutron light yield of \sim 245000 photons. The decay times for neutrons are faster compared to that for gamma-rays, hence we achieved good pulse shape discrimination (PSD) between gamma and neutron events. Our initial studies on the effects of Eu concentration on the properties of LSI show that 3%–4% Eu concentration is optimal for the best performance in terms of gamma and neutron light yields and pulse shape discrimination. LCI shows the main emission at \sim 475 nm under X-ray excitation and a very high gamma light yield of \sim 90000 photons/MeV. The measured energy resolution is 6% at 662 keV. The electron equivalent energy for neutron detection has been measured to be around 3 MeV, which gives a neutron light yield of \sim270000 photons. The measured decay times for neutrons are faster compared to gamma decays and the PSD between the gamma-rays and neutrons is not as good as LSI. LSB shows two emissions at \sim 410 and 475 nm under X-ray excitation. The measured light yield is \sim 32000 ph/MeV gamma-ray with an energy resolution of 6% at 662 keV. The electron equivalent energy of the ^6Li capture peak was measured to be 3.3 MeV. [ABSTRACT FROM AUTHOR]