Spectral Performance of Ce:GAGG Scintillators

To evaluate the spectral performance, we prepared 5 × 5 mm² unpolished as-cut samples of varying thicknesses (2, 5, 10, and 20 mm) sawed from a larger (5 × 5 × 50 mm³) unpolished Ce:GAGG single-crystal block (TPS, Republic of Korea) grown by the Czochralski technique. The mechanically polished reference samples were prepared using a polisher (XP 8, Ted Pella) with alumina suspension (particle size: 1 μm). The chemically polished samples were fabricated by dipping the as-cut samples into a beaker containing phosphoric acid (85% in volume), placed in a silicone oil bath, to evaluate the effect of chemical polishing on the light output of the crystal samples [11 (link), 12 (link)]. First, to investigate the correlation between the chemical polishing time and the etching rate, groups of 5 × 5 × 2 mm³ Ce:GAGG single-crystal samples were etched separately for 5, 10, 20, 30, 60, 90, and 120 min. As described before, the transmittance of the scintillation light to the photosensor is also dependent on the crystal thickness; thus, the Ce:GAGG single-crystal samples of 2, 5, 10, and 20 mm thicknesses were chemically polished for 30, 60, 90, and 120 min to compare their light outputs. The two polishing methods and spectral data acquisition process are illustrated in Fig 1. After the chemical polishing, each sample was cleaned with deionized water and dried in air. Next, the change in the weight of each sample was recorded to assess the weight loss due to chemical polishing.