PSI - Issue 79

George Papageorgiou et al. / Procedia Structural Integrity 79 (2026) 138–145

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2.3. Luminescence Efficiency In order to obtain the luminescence efficiency of the three crystals, the X-ray exposure data and the light energy flux were measured. These data were combined using equation (1): � � � � � � � �� ���� � � � � � �� , (1) � � represents the light energy flux (units: μ W/m 2 and the exposure rate ( � � (units: mR/s). In this sense, AE has units ( μ W/m 2 )/(mR/s), denoted by the initials EU. The rest of the parameters shown in equation (1) can be depicted from Figure 2 [17].

Fig. 2. The experimental set-up for the luminescence efficiency of the three examined crystals.

3. Results and Discussion Figures 3-5 show the PMT readings converted to voltage, versus time and temperature. All signals are shown within the 1 second time frame that was set in the X-ray tube for the irradiations. In this period, the signal of the excited crystals rises up to a plateau and when the irradiation stops, signal drop off can be noticed. It can be depicted that as the temperature rise, the voltage reading drops for all three crystals, however with different rates [18]. Higher voltage values are shown for the LSO:Ce crystal (ranging from 0.43 to 0.9 V), in accordance with the light yield data of the literature (Table 1). LYSO:Ce reached maximum voltages values in the range from 0.21 to 0.65 V. Irradiation of the GSO:Ce results to the lower voltage values (0.24 to 0.34 V), as a consequence of its light yield values that ranges around 10 3 photons/MeV.