Study of timing properties of silicon photomultipiers

A new setup has been made at Fermilab for detector timing measurements at picosecond level. The core timing resolution of the amplifiers, discriminators and TAC/ADC combination is approximately 2 picosecond. We have made a study of a single photoelectron time resolution (SPTR) measured for signals coming from silicon photomultipliers (SiPm) made by different manufacturers. The obtained SPTR is of the order of 180 picosecond with SiPms illuminated by red (635 nm) PiLas laser light. IRST SiPms show better SPTR when illuminated by the blue laser light (405 nm). Most of the data were taken with 1 Volt of the overvoltage. The SiPms time resolution is inversely proportional to the square root of the number of photoelectrons. A time-of-flight (TOF) system with few tens of picosecond time resolution, based SiPms with quartz Cherenkov radiators looks practically achievable. A simple model is proposed to explain the difference in SPTR of the IRST SiPms when illuminating by the blue and red light. The explanation of the origin of the tail in the MPPC SiPm's single photoelectron time spectra is presented. Finally, requirements for the SiPms temperature and bias voltage stability to maintain few picosecond time resolution are discussed.