Abstract
Silicon photomultipliers (SiPMs) have become an interesting alternative to conventional and micro-channel plate photomultipliers, proving to be a very good option for Cherenkov light based time-of-flight detectors. The important characteristic for this application is the intrinsic time resolution for a wide range of wavelengths (from below 250 nm up to about 600 nm).
We present a study of the time resolution of two SiPMs: a 3 x 3 mm(2) FBK SiPM-NUV3S and a 3.5 x 3.5 mm(2) STMicroelectronics prototype SiPM. The measurement was performed for two representative wavelengths (280 nm and 420 nm) under the variation of SiPM overvoltage and light intensity.
The measured transition time spread (TTS) of the devices was (285 +/- 9) ps (FBK) and (154 +/- 20) ps (STM). The time resolution dropped with increasing mean number of photoelectrons (N-pe) as sigma N-TTS(pe)-1/2 with saturation observed for high N-pe.
The obtained best time resolutions were (8 +/- 1) ps and (4 +/- 1) ps for the FBK and STM SiPM respectively at N-pe of the order of 10(6) for 420 nm photons. The results for the two wavelengths were comparable, with 280 nm photons providing worse results at very high illumination.