[Dong Huasong] China Univ Petr, Dept Comp Sci & Technol, Beijing 102249, Peoples R China
; [Wu Chong] China Univ Petr, Dept Math & Phys, Beijing 102249, Peoples R China
; [Sun Zhijia] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
With the technology of coincidence method, transit time spreads (TTSs) of PMTs are measured with Cherenkov light on the photocathode window of photomultiplier tube (PMT) produced by cascade gamma radiation source, (60)Co. TTSs with single and multi-photoelectron which are analyzed by convolution of Poisson and Gaussian are obtained. The study to XP2020 and XP2020Q PMTs shows that TTSs are consistent with data supplied by Philips. TTSs are inversely proportional to the square roots of number of photoelectrons. The method is feasible when single and multi-photoelectron can be distinguished.