Alpha and gamma spectroscopy of composite scintillators based on the LuAG:Pr crystals and single crystalline films of LuAG:Ce and (Lu,Gd,Tb)AG:Ce garnets

Alpha and gamma spectroscopy (pulse height spectra and scintillation decay time profiles) were used to study scintillating properties of composite scintillators systems consisting of single crystalline films (SCF) and single crystal (SC) substrate plates. α-particles of $^{241}$Am of energy 5.4857 MeV and γ-quanta of $^{137}$Cs of energy 661.66 keV are used as excitation sources of SCFs or SC substrates, respectively. As SC substrates mainly LuAG:Pr single crystal plates are used and these plates are characterized by light yield (LY) between 10-21 × 10$^{3}$ ph/ MeV, Energy Resolution (ER) ~5% at 661.66 keV and good proportionality. LuAG:Ce, Lu$_{2}$$_{-}$$_{x}$GdTb$_{x}$AG:Ce and Lu$_{3}$$_{-}$ $_{x}$Tb$_{x}$AG:Ce SCFs at x = 0.15–2.285 were prepared by LPE method onto LuAG:Pr substrates and investigated. LY of LuAG:Ce SCF under α-particles excitation is about of 60% than that of LuAG:Pr SC substrate. The LY of Lu$_{3-x}$ Tb$_{x}$AG:Ce SCFs depend nonlinearly on Tb$^{3+}$ concentration in the 0.15–2.285 range and changed from 60-62% to 106–109%, respectively, in comparison with LY of LuAG:Pr SC substrate. Detailed scintillation decay time profiles have shown that there are differences between the decay curves of composite scintillators under α- particles and $\gamma$-quanta excitations. Such differences are characterized using the tα/t$\gamma$ ratio between the time of scintillation decay to 1/e, 0.1, 0,05 and 0.02 levels under α-particles excitation (t$_{α}$) and $\gamma$-quanta excitation (t$\gamma$). From all studied types of composite scintillators, based on the LuAG:Pr substrates, the highest value of t$_{α}$/t$\gamma$ ratio can be reached for Lu$_{3-x}$Tb$_{x}$AG:Ce SCF/LuAG:Pr SC substrate composite scintillators at Tb content x = 2.15–2.275, where this ratio is equal to 4.2–6.2 at scintillation decay level of 0.1.