The invention relates to a characterization apparatus (1) for characterizing scintillator material (3) especially for a PET detector. A first radiation source (2) irradiates the scintillator material with first radiation (4) having a wavelength being smaller than 450 nm. Then, a second radiation source (5) irradiates the scintillator material with pulsed second radiation (6) having a wavelength being larger than 600 nm and having a pulse duration being equal to or smaller than 50 s, wherein a detection device (9) detects third radiation (12) from the scintillator material (3) during and/or after the irradiation by the second radiation. The third radiation depends on the amount of charge carriers trapped at electronic defects of the scintillator material such that it can be used as an indicator for the amount of electronic defects and hence for characterizing the scintillator material. This characterization can be performed relatively fast and in a relatively simple way.