PSI - Issue 79

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

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The intrinsic characteristics of LYSO:Ce and LSO:Ce have small differentiations due to the variable percent of Yttrium in the mixture. The density of LYSO:Ce is 7.15 g/cm 3 whereas the corresponding value for LSO:Ce is 7.4 g/cm 3 . While GSO:Ce has lower density, with a value of 6.7 g/cm 3 , offer a reasonable light yield and stability under various conditions, making it suitable for cost-effective imaging applications [2]. Both LSO and LYSO have close effective atomic numbers, decay times and energy resolution. The light yield of LSO can reach higher values than LYSO. All three materials have almost equal mineral hardness, their emission maximum lies in the same optical wavelength region and are not hygroscopic. 2.2. Experimental set-up Figure 1 presents the three investigated single crystals (10×10×10 mm). The crystals have polished surfaces as it can be seen in the middle sample of Figure 1. For crystal irradiation, a conventional radiological X-ray system was employed, consisting of a DR 200 CMP CPI X-ray unit paired with an RTM90HS SpA IAE X-ray tube, operated at 90 kVp and 63 mAs with the large focus of 1.2 mm. The distance between the X-ray source and the samples was maintained at 0.725 m, and a 20 mm external aluminum filter was positioned in the output of the tube [7] . The samples were positioned at the input of the integrating sphere (Oriel-70451), and the luminescence generated after the X-ray excitation was detected using a photomultiplier tube (9798 EMI) having an extended sensitivity (S20) photocathode. Dosimetry was carried out with a calibrated digital dosimeter (RTI/Piranha/P100B). The PMT operated under a 22 V potential between the S20 and the initial dynode (with all dynodes shorted). Temperature control for the crystals, within the 16°C to 171°C range, was achieved by adjusting a thermocouple to the sample surface using Teflon tape, leaving exposed only one face in order for the produced light to escape the crystal, towards the internal of the integrating sphere (as shown in Figure 1 with the two crystal on the left and right). Heating was provided by a Perel model 3700-9 heat gun. Temperature measurements were recorded using a digital multimeter (Agilent-Technologies/U1253A), paired with a thermocouple (U1185A) and an appropriate temperature sensor [17].

Fig. 1. The three examined crystal. Wrapped with Teflon (left, right), unwrapped (middle).