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The Mg co-doping in Ce-activated garnet scintillators has shown several highly beneficial effects, such as acceleration of the scintillation decay or improved afterglow, while the LY remains sufficiently high [1]. Excellent scintillation properties have recently been reported in garnet epitaxial films GAGG:Ce,Mg grown by liquid phase epitaxy [2].
In this work, the effect of Mg2+ co-doping on timing characteristics is studied in (Lu0.8Gd2.2)(Al2.5Ga2.5)O12:Ce and Lu3Al5O12:Ce garnet films. The films were grown by liquid phase epitaxy from the lead-free BaO-B2O3-BaF2 flux. The kinetics of scintillation emission was studied under X-ray excitation pulse with FWHM of 620 ps. The results are quantitatively compared with those obtained by e-beam and optical excitations. Significant improvements of timing performance of the Mg2+ co-doped garnet scintillators have been observed, namely a substantial shortening of the rise time and acceleration of the scintillation decay. In particular, the rise time in GAGG:Ce,Mg decreased from 400 ps in Mg-free sample to 70 ps in the sample with 700 ppm Mg (values refer to the rise of the signal from 10 to 90 %). Furthermore, the signal decreases to only 0.07 % just at 1 microsecond after the X-ray pulse excitation and the scintillation decay to 1/e value accelerated from 70 to 15 ns in Mg co-doped samples. Any notable delay was not observed under optical excitation into the 5d1 absorption band. Similar improvements of the timing properties were also observed in LuAG:Ce,Mg.
Such excellent timing properties makes these garnet films competitive candidates for high rate imaging techniques or for the electron detectors in e beam devices.
[1] M. T. Lucchini, V. Babin et al., Nucl. Instrum. Methods A 816, 176 (2016).
[2] P. Prusa, M. Kucera et al., Adv. Optical Mater. 5, 1600875 (2017).
