W. Chewpraditkul

Luminescence properties and scintillation response in Ce3+-doped Y2Gd1Al5-xGaxO12 (x = 2, 3, 4) single crystals

The compositional dependence of luminescence properties and scintillation response were investigated in Ce3+-doped Y2Gd1Al5-xGaxO12 (x = 2, 3, 4) single crystals. The Gd3+ → Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. With increasing Ga content in the garnet host, the Ce3+ luminescence from the lowest 5d level (5d1) is shifted toward higher energy due to the decrease in the crystal field splitting of the 5d levels. Light yield (LY) and its dependence on the amplifier shaping time were measured under excitation with γ-rays. High LY value of ∼38 000 ph/MeV was obtained for a Y2Gd1Al3Ga2O12:Ce sample. Scintillation decay was measured with an extended dynamical and temporal scale under the nanosecond pulse soft X-ray excitation. The decrease of both LY value and relative contribution of slower decay component in the scintillation response was observed with increasing Ga content in the garnet host.

Nonproportionality of electron response using CCT: plastic scintillator.

The scintillation response of a plastic scintillator (NE102) has been characterized using compton coincidence technique. The coincidence technique allowed detection of nearly monoenergetic internal electrons resulting from the scattering of incident 662keV gamma-rays within a primary NE102 detector. Scattered gamma-rays were detected using a secondary NaI(Tl) detector in a coincidence mode. The electron response nonproportionality of NE102 plastic scintillator was measured using this technique for electron energies ranging from 28 to 436keV, by varying the scattering angle. The NE102 showed a good proportionality of light yield within 3% at energies between 90 and 436keV. Below 90keV, the light yield decreases by about 20% upon lowering the electron energy to 28keV. The electron energy resolution of NE102 was also measured using this technique in the energy range from 68 to 436keV. It has been found that the energy resolution varies from 25.2% at 68keV to 11.8% at 436keV.

Physical, Structural and Luminescence Properties of ZnO-Bi2O3-B2O3 Glass System

The ZnO-Bi2O3-B2O3 (ZBB) glasses with different concentrations of Bi2O3 have been prepared by a conventional melt quenching technique and investigated the effect of Bi2O3 on the physical, structural and luminescence properties. The density and hardness of glasses are also measured and found to increase with increase of Bi2O3 concentration. The IR studies indicate that these glasses are made up of [BiO3], [BO3], [BO4] and [B basic structural units. From optical spectra, the cut-off wavelengths were shifted from 423 nm to 447 nm as the content of Bi2O3 increases from 15 to 30 mol%. The photoluminescence spectra exhibit characteristic peaks at 602 nm corresponding to 3P11S0 transitions of Bi3+. The decay time for 3P1 level of Bi3+ increases with increase of Bi2O3 concentration.

Scintillation properties of praseodymium doped LuAG scintillator compared to cerium doped LuAG, LSO and LaBr

Properties of praseodymium and cerium doped Lutetium Aluminum Garnet (LuAG) were compared with cerium doped Lutetium Oxyorthosilicate (LSO) and Lanthanum Bromide (LaBr 3 ). Light yield, its non-proportionality relative to 662 keV γ-rays and the dependence of the energy resolution on energy of the detected γ-rays were measured. LuAG:Pr turned out to have good proportionality, with deviation from unity around 10% at 16.6 keV and 3% at 59.5 keV. This, together with relatively high light yield of 5600 phe/MeV results in a very good energy resolution of LuAG:Pr of 5.1% measured with 662 keV γ-rays. Coincidence time resolution was measured to be 308 ps, significantly larger than that of LSO:Ce - 166 ps. This can be explained by smaller light yield of LuAG:Pr and the fact that only around 25% of its scintillation is emitted in short decay time modes of 17.6 ns and 52 ns, while the rest is decaying with long time modes of 1.4 μs and 9 μs.

Luminescence and Light Yield in Ce3+-Doped Y1Gd2Al5-xGaxO12 (x=2,3,4) Single Crystal Scintillators

The compositional dependences of luminescence properties and light yield were studied in Ce3+ -doped Y1Gd2Al5-xGaxO12 (x = 2, 3, 4) single crystal scintillators. The Gd3+→ Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. With increasing Ga content in the garnet host, the Ce3+ luminescence from the lowest 5d level (5d1) was blue-shifted due to the decrease in the crystal field splitting of the 5d levels. High light yield (LY) value of ~36,000 ph/MeV was obtained for a Y1Gd2Al2Ga3O12:Ce sample under excitation with 662 keV γ-rays. The decrease of LY value was also observed with higher Ga content due to the thermal ionization from the 5d1 level to the conduction band.

Effects of Ga Content on Optical and Scintillation Properties in Ce3+-Doped YGd2(Al,Ga)5O12 Scintillators

The optical and scintillation properties of Ce3+-doped YGd2(Al,Ga)5O12 single crystal scintillators were investigated. The Ce3+ 5d-4f emission was blue-shifted with increasing Ga content due to the decrease of the crystal field strength. Temperature dependence of the photoluminescence decay times was measured and the thermal activation energy for the luminescence quenching was calculated. Light yield (LY) and its dependence on an integration time were measured under γ-ray excitation. The fast component content in the scintillation response increases with increasing Ga content. The YGd2Al2Ga3O12:Ce sample showed a high LY of 38,000 photons/MeV. The decrease of LY value observed for a YGd2Al1Ga4O12:Ce sample is mainly due to the thermal ionization of the 5d1 excited state of the Ce3+ emission center to the conduction band.