Upgrade of End-cap TOF trigger system on BESIII

Abstract

In the ETOF(End-cap TOF) upgrade of BESIII, MRPC(Multi-gap Resistive Plate Chamber) detectors are used. ETOF is designed with 72 MRPCs. 24 channels signal are read out from each MRPC, in which 6 neighbouring channels OR together in Front-End Electronic(FEE) side. So 288 channel hit signals are sent to ETOF trigger system for trigger logic. The MPRC hit signal is about 30 ns width after FEE. Hit signals are stretched and trigger data are stored by TDPP (Trigger Data Pre-Processor) and then sent to ETOFT (End-cap TOF Trigger) through 10 high speed optical fiber links. Trigger data are aligned and stored in FIFO in ETOFT. Trigger logic in the center FPGA counts hit signals and finds Back to Back (BtB) events and give out three ETOF trigger conditions: NETOF.GE.1, NETOF.GE.2 and ETOF.BB. ETOF trigger conditions are integrated with other detector trigger signals by SIF2(Signal Integrate and Fan-out Version2) to Global Trigger to generate L1. ETOF trigger system was installed on BESIII in Sept.2015 and has run stable for half year.