We have studied the performance of a doublelayer TOF unit, which is made of
tw BC408 scintillators coupled directly with high antimagnetic R2490-05 PM
Ts. The experimental results using a 2GeV pi(-) beam show that its time res
olution is less than 50ps. With the good time resolution, simple constructi
on, mature technique and low price, the TOF detector composed of the unit s
tudied herein is capable to be applied in the PID system in the tau-c facto
ry.