Physical characterization of the LabPET™ LGSO and LYSO scintillators

The luminescence and nuclear spectroscopic properties of LGSO (Lu_0.4Gd_1.6SiO₅:Ce) and LYSO (Lu_1.9Y_0.1SiO₅:Ce) crystals used in the LabPETtrade scanner were investigated. UV-excited luminescent spectra outline similarities with typical cerium-doped oxyorthosilicate scintillators but distinguish themselves by definite secondary emissions at near infrared wavelength. The two distinct luminescence mechanisms Ce1 and Ce2 previously identified in other cerium-doped oxyorthosilicate crystals appear to be present in the LYSO and LGSO scintillators used in the LabPETtrade. The intrinsic light yield, energy resolution and coincidence time resolution were assessed. The intrinsic light yield of LGSO relative to LYSO is 54% plusmn 1% when detected with PMT and 65% plusmn 5% with APD. The energy resolution obtained with APD attains 16.6% plusmn 0.6% for LGSO and 14.0 plusmn 0.4% for LYSO. Coincidence time resolutions of 1.8 and 3.0 ns FWHM were measured with APD in reference to a fast PMT-plastic detector for the LYSO and LGSO, respectively.