O. Sidletskiy

Growth and luminescent properties of Lu2SiO5 and Lu2SiO5:Ce single crystalline films

Single crystalline films (SCF) of Lu2SiO5 (LSO) and Lu2SiO5:Ce (LSO:Ce) silicates with thickness of 2.5-21 μm were crystallised by liquid phase epitaxy method onto undoped LSO substrates from melt-solution based on PbO-B2O3 flux. The luminescence and scintillation properties of LSO and LSO:Ce SCFs were compared with the properties of a reference LSO:Ce and LYSO:Ce crystals. The light yield (LY) of LSO and LSO:Ce SCF reaches up 30 % and 145 %, respectively, of that of a reference LSO:Ce crystal under excitation by α-particles of 241Am source (5.5 MeV). We found that the luminescence spectrum of LSO:Ce SCF is red-shifted with respect to the spectrum of a reference LSO:Ce crystal. Differences in luminescence properties of LSO:Ce SCF and single crystal are explained by the different distribution of Ce3+ over the Lu1 and Lu2 positions of LSO host and are also due to Pb2+ contamination in the former.

Phenomenological approach to prediction of scintillation yield in mixed crystals

Behavior of light yield in wide range of inorganic scintillation crystals formed by isovalent substitution of anions or cations is summarized. The correlations between improvement of light yield in mixed crystals, and the ratios of ionic radii and atomic weights of the substituted atoms, as well as the bandgap difference between the components of mixed crystal, have been analyzed. It is presumed that non-monotonous dependence of light yield on components ratio in mixed scintillators is called by modulation of energy structure and limitation of carrier migration length due to spatial inhomogeneity in crystal. Phenomenological approach to prediction of light yield in mixed scintillation crystals has been proposed.

Energy Relaxation in LSO and LGSO Crystals Studied in the VUV Range

The role of energy transfer from Gd3+ to Ce3+ activator in the formation of the luminescence yield and kinetics of Lu2xGd2-2xSiO5:Ce (LGSO) mixed crystals has been studied by VUV spectroscopy including temperature dependent time-resolved measurements of luminescence excitation and emission spectra and luminescence kinetics in the excitation energy range 4 to 25 eV at the SUPERLUMI station of HASYLAB, DESY. Improved scintillation yield as well as suppressed afterglow that can be achieved by appropriate choice of Lu/Gd ratio as well as of Ce-concentration were suggested to result from an additional channel of energy relaxation via Gd-states, which appears in LGSO. The role of Ca-codoping is discussed.

Epitaxial growth of composite scintillators based on Tb3Al5O12 : Ce single crystalline films and Gd3Al2.5Ga2.5O12 : Ce crystal substrates

This work presents our latest achievements in the development of advanced composite scintillators for simultaneous registration of α-particles and γ-quanta in mixed ionizing fluxes based on single crystalline films (SCFs) of Tb3Al3O12u2006:u2006Ce (TbAGu2006:u2006Ce) garnet and Gd3Al2.5Ga2.5O12u2006:u2006Ce (GAGGu2006:u2006Ce) single crystal (SC) substrates using the liquid phase epitaxy (LPE) growth method from a melt-solution based on a PbO–B2O3 flux. The separation of the signals from the SCF and SC components of such composite scintillators can be realized by means of registration of the difference in the scintillation decay times of SCF and substrate scintillators and can be achieved at a large K = t(SCF)/t(SC) ratio, which is usually above 2. The TbAGu2006:u2006Ce SCFs exhibit relatively fast scintillation response under α-particle excitation with decay times of t1/e = 344–380 ns and t1/100 = 3130–3770 ns. Meanwhile, the scintillation response of TbAGu2006:u2006Ce SCFs under α-particle excitation is significantly slower in the 500–4000 ns range than that of the GAGGu2006:u2006Ce crystals with decay times of t1/e = 270–280 ns and t1/20 = 1280–1300 ns. We have found that for TbAGu2006:u2006Ce/GAGGu2006:u2006Ce composite scintillators, the optimal K ratio changes from 2.0 to 3.0 at the registration of scintillations with shaping times of 700–4000 ns. For this reason, TbAGu2006:u2006Ce/GAGGu2006:u2006Ce composite scintillators possess the best scintillation properties among all known LPE grown analogues for simultaneous registration of α-particles and γ-quanta in mixed fluxes.

Scintillating screens based on the single crystalline films of orthosilicates and multicomponent garnets

The report presents our achievements in the creation of scintillating screens for micro-imaging based on the single crystalline films of (Lu,Y)₂SiO₅ orthosilicates and (Lu,Gd)₃(Al,Ga)₅O₁₂:Ce multicomponent garnets using the Liquid Phase Epitaxy (PLE) method.