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The temperature dependence of scintillation decay and rise time was measured for GGAG:Ce and Ca-codoped GGAG:Ce crystals in the temperature range of 10 K to 400 K. The decay and rise times were found to increase with decreasing temperature in the case of GGAG:Ce crystals, while Ca codoping modifies the kinetics such that decay and rise times are constant with the change in temperature. In order to obtain a better understanding of the role of trap centers in the temperature dependence of scintillation kinetics, spectrally resolved thermoluminescence (TL) properties were also studied for these crystals. [ABSTRACT FROM PUBLISHER]

This paper investigates the effects of boron and calcium co-doping on the measured energy resolution of Gd3Ga3Al2O12:Ce (GGAG: Ce). For this study, three samples of GAGG were grown using the Czochralski method. The first sample was doped with Ce^3+ and was used as a reference for comparison. The next two samples were additionally doped with either B^3+ or Ca^2+. The boron co-doped sample was found to have an overall improved performance when compared to the reference sample. The light output of the GGAG:Ce,B was measured to be 10% greater than the reference sample. In addition, the sample was found to have less charge trapping and a more linear relative light yield response. These factors led to an observed improvement in energy resolution from 9% in the reference sample to 7.8% in the B^3+ co-doped sample. Co-doping with Ca^2+ led to an overall reduction in charge trapping; however, the sample suffered a 30% reduction in light output, and it was found to have a less linear relative light yield than the reference sample. Its energy resolution was measured to be 10.1%. The relationship between the measured energy resolution and the other measured properties in these samples is discussed. [ABSTRACT FROM AUTHOR]

The temperature dependence of the photoluminescence properties of Gd2SiO5:Ce,Ca crystals was found to be significantly affected by Ca codoping and shows that presence of additional energy levels in these crystals provides nonradiative energy transfer. The excitation and emission bands also broaden with codoping due to presence of these additional energy levels. Therefore Ca codoping in Gd2SiO5 crystals decreases the scintillation decay very strongly and has a strong adverse affect on scintillation light yield, different from the effect in other members of the oxyorthosilicate family such as Lu2SiO5 and Y2SiO5. [ABSTRACT FROM PUBLISHER]

Experimental studies of LSO:Ce crystals co-doped with various concentrations of Ca are presented. Photoluminescence decay time, excitation and emission spectra, thermal response and X-ray excited luminescence are investigated as a function of Ca concentration. Experimental data show Ca co-doping does not alter the energy level structure of either Ce1 or Ce2, but reduces the relative population of Ce2 to Ce1. Thus, the luminescence from Ce2 is suppressed, which contributes to the fast scintillation decay of Ca co-doped LSO:Ce. [ABSTRACT FROM AUTHOR]

A comparative study of five 5 x 5 x 5 mm³ LSO:Ce samples with different co-dopings of calcium, from 0 to 0.4% is reported. All the results are compared to those obtained with selected 10 x 10 x 5 mm³ LSO crystal, tested in previous studies. The influence of Ca co-dopant on scintillator parameters was studied using a Photonis XP20D0 fast timing photomultiplier. The tests included measurements of light output in terms of number of photoelectrons, measurements of time resolution in coincidence experiments with annihilation quanta from a 22Na gamma source, and decay time constant calculations on the basis of timing spectra obtained using the Bollinger-Thomas single photon method. Also energy resolution for 662 keV from 137Cs gamma source is mentioned at the end of the paper. The results showed the significant influence of the Ca co-dopant on the properties of the LSO scintillators. For low Ca concentrations of 0.1%, photoelectron number and energy resolution were improved up to 7800 phe/MeV and 7.3% respectively. On the other hand the shortest decay time constants were obtained for higher concentrations of 0.3% and 0.4% of Ca giving values equal to about 30 ns. The time resolution improvement was similar for all the samples and calculated values for a single detector were equal to about 140 ps. [ABSTRACT FROM AUTHOR]