Performance of a novel, small-cell, high-fill-factor SiPM for TOF-PET

In this paper, we present a novel SiPM technology, developed at FBK, characterized by small cells with very high fill factor, called RGB-HD (red-green-blue high-density SiPM). The first prototypes feature a cell size of 15×15 μm² and 30×30 μm² with nominal fill factors of 48 % and 75 %, respectively. Here we focus on the 30 μm cell size, which was used to produce a 4×4mm² SiPM. We coupled different samples to both LYSO and GAGG scintillators, with sizes of 3×3×5 mm³ and 4×4×22 mm³, in order to characterize the RGB-HD SiPM performance for TOF-PET application. The results are extremely promising. We measured energy resolution of 9 % and coincidence resolving time of 170 ps FWHM with thick LYSO while 7 % and 375 ps FWHM with thick GAGG.