Scintillation properties and timing performance of state-of-the-art Gd 3 Al 2 Ga 3 O12 single crystals

Future colliders will set stringent requirements on the performance of detector materials in terms of timing and radiation hardness. Scintillating garnet crystals proved to satisfy the latter, while the former can be improved through technological developments. In this work, optical and scintillation properties of Cerium-doped Gd${}_3$Al${}_2$Ga${}_3$O₁₂ (GAGG:Ce) single crystals were studied upon gamma radiation excitation. Several 2x2x3 mm${}^3$ and 2x2x10 mm${}^3$ samples from various producers were characterized in terms of light output, transmission, scintillation kinetics and coincidence time resolution (CTR). Light output was measured using a ¹³⁷Cs radioactive source, ranging between 27900 and 49500 photons per MeV. Scintillation emission time profiles were measured with 511 keV gamma excitation, and the fastest samples displayed components below 70 ps rise time and 50 ns decay time. CTR was measured employing silicon photomultipliers (SiPMs) obtaining a best value of 87 $\pm$ 2 ps full width at half maximum, significantly improving on past state-of-the-art GAGG.