The Ce3+ activated Y3Al5O12 (YAG:Ce) is a fast and efficient inorganic scintillator widely used in electron and X-ray detection systems. The single crystals of YAG:Ce achieve 90-120 ns decay constant of the scintillation pulse and light yield up to 30 000 photons/MeV. In previous studies, we have shown that RE3+ codoping of YAG:Ce and the associated resonant energy transfer from Ce3+ to RE3+ codopant enables acceleration of the Ce3+ photoluminescence decay [1,2].
In this work, the application of the time-resolved X-ray spectroscopy on the measurement of fast processes of the scintillation phenomena will be presented. The setup, consisting of a laser-driven picosecond X-ray excitation source (Hamamatsu) and a fast detection system (Horiba), was used for the current study. The X-ray pulses are generated by the laser with a variable repetition rate and delivered to the sample located near the exit window of the X-ray tube. The luminescence produced by the sample is guided directly to the entrance window of the hybrid PMT through a collecting lens. The acquisition of the data is performed by the time-correlated single photon counting technique. The temporal resolution is defined by the instrumental response function of the setup and the corresponding full width at half maximum which is about 66 ps, see Fig. 1.
In the current study, we exploit the ultrahigh temporal resolution of the described setup for the measurement of the scintillation decay curves of the RE3+ codoped YAG:Ce. Specifically, we focus on the initial part of the decay where the RE3+ codoping induces a shortening of the rise time of the scintillation pulse, see Fig. 1.
 M. Pokorný et al., Opt. Mater., 86 (2018) 338.
 J. Páterek et al., J. Lumin., 213 (2019) 469