Single photon time resolution with silicon photomultipliers using the STiC readout chip

STiC3 is a mixed mode Application Specific Integrated Circuit (ASIC) for high resolution timing readout of Silicon Photomultipliers (SiPMs). It is designed for Time-ofFlight (ToF) applications in medical imaging and High Energy Physics experiments and has been developed in the framework of EndoToFPET-US project. The STiC3 chip uses the UMC 180 nm CMOS technology and has a differential structured front-end to reject common-mode noise. It has 64 channels and each channel consists of an analog front-end, a build-in TDC module and a digital part. In earlier measurements using 3.1×3.1×15 mm3 LYSO crystals and Hamamatsu S10362-33-050C MPPC sensors, a Coincidence Time Resolution (CTR) of ~214 ps FWHM has been obtain; the achieved energy resolution is ~12 % for 511 keV photons. In order to explore the timing performance for small signals a special setup has been established in our laboratory. The setup includes an optical system for automatically focusing a laser beam to a spot size smaller than 3 μm and allows to precisely evaluate the performance of the STiC3 chip as well as to carry out SiPMs characterization studies. A first measurement of the Single Photon Time Resolution (SPTR) using STiC3 is presented in this paper.