Performance of FBK high-density SiPM technology coupled to Ce:LYSO and Ce:GAGG for TOF-PET

This paper presents the performance, in terms of energy and timing resolution, of high-density silicon photomultipliers (SiPMs) produced at Fondazione Bruno Kessler for time-of-flight positron emission tomography application. The new SiPM technology allows us to produce devices with a small cell size maintaining a high fill factor (FF). The sensors considered in this paper are composed by 30x30 mu m(2) cells with a FF exceeding 70% to cover a total area of 4x4mm(2). The SiPM performance was evaluated using two types of scintillators (Ce:LYSO and Ce:GaGG) both with a short height (5 mm) in order to minimize the time jitter caused by light propagation in the crystal. With Ce: LYSO, an energy resolution of 9.0% FWHM at 511 keV and a coincidence resolving time (CRT) of 125 ps FWHM were obtained at -20 degrees C. With Ce: GaGG, an energy resolution of 6.4% FWHM and a CRT of 260 ps FWHM were achieved at the same temperature. The novel SiPM technology, combining a high PDE with a low correlated noise (i.e., crosstalk and afterpulse), allows us to improve the state-of-the-art of energy and timing resolution with both the tested crystals.