Multi-channel digital SiPMs: Concept, analysis and implementation

This paper presents a comprehensive statistical analysis of timing resolution in a digital silicon photomultiplier (DSiPM) when multi timestamp is available. We look at the effect of dart count rate (DCR) on timing resolution in these devices as compared to analog silicon photomultipliers (A-SiPMs). The analysis includes photon detection efficiency (PDE), DCR, electrical jitter of the detector with a LYSO crystal. Timing resolution is analyzed utilizing a single timestamp or multiple timestamps. Simulation results show that D-SiPMs utilizing multiple timestamps (Multi-channel D-SiPM) can be more tolerant to DCR than those utilizing a single timestamp. The timing resolution is 13%, 20% and 40% better at 1000 detected photons, 200 ps rise time and 40 ns decay time of a LYSO scintillator, without DCR, with 1 MHz DCR and with 10 MHz DCR, respectively. Based on these findings, we propose new architectures to acquire multiple timestamps without sacrificing fill-factor. This paper also includes the implementation and characterization of 4 × 4 Multichannel D-SiPMs coupled with an array of 44ps LSB TDCs for coincidence detection of gamma rays. The pitch of the SiPMs is 800 μm and the number of pixels in one SiPM is 416. The pixel has a 57% fill factor with 121 ps timing resolution for a single photon. The SiPM timing resolution for single photon detection is 179 ps FWHM.