Exploring Large-Volume GAGG Scintillators for use in MeV Gamma-Ray Astrophysics

Gamma-ray astrophysics in the MeV band is an exciting field in astronomy due to its potential for multi-messenger astrophysics. It has, however, remained under-explored when compared to other wavelengths. One reason for this observational gap is the difficulties with measuring these high-energy photons and the requirement of large amounts of detection material. In this work, we investigate the usage of large-volume GAGG scintillators for use as a calorimeter in future MeV telescopes. We developed a 5×5 array calorimeter utilizing 1×1×6 cm^3 GAGG crystals with C-series SiPM readout. The calorimeter was tested at the High Intensity Gamma-ray Facility (HIGS) with monoenergetic beams ranging from 2-25 MeV. Finally, we also investigated larger 1×1×8 cm^3 crystals and characterized their response across their depth when their surface treatment is either polished or frosted.