Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
; Univ Hawaii, Honolulu, HI 96822 USA
; KEK, Natl Lab High Energy Phys, Tsukuba, Ibaraki 305, Japan
We have studied the performance of a doublelayer TOF unit, which is made of tw BC408 scintillators coupled directly with high antimagnetic R2490-05 PMTs. The experimental results using a 2GeV pi(-) beam show that its time resolution is less than 50ps. With the good time resolution, simple construction, mature technique and low price, the TOF detector composed of the unit studied herein is capable to be applied in the PID system in the tau-c factory.