Cao Ping, Sun Wei-Jia, Ji Xiao-Lu, Fan Huan-Huan, Wang Si-Yu, Liu Shu-Bin, An Qi
The prototype of time digitizing system for the upgrade of BESIII endcap TOF (ETOF) is introduced in this paper. The ETOF readout electronics has a formation of distributed architecture that hit signal from multi-gap resistive plate chamber (MRPC) is signaled as LVDS by front-end electronics (FEE) and sent to the back-end time digitizing system via long shield differential twisted pair cables. The ETOF digitizing system consists of 2 VME crates each of which contains modules of time digitizing, clock, trigger and fast control etc. The time digitizing module (TDIG) of this prototype can support up to 72 electrical channels of hit information measurement. The fast control (FCTL) module can operate at barrel or endcap mode. The barrel FCTL fans fast control signals from the trigger system out to endcap FCTLs, merges data from endcaps and transfers to the trigger system. The digitizing architecture can meet the requirements of ETOF upgrade nearly without modifying the original TOF structure and can benefit for improving ETOF performance without degrading others. Lab and beam experiments show that the time measuring resolution without FEE can be better than 20ps and the data transmitting rate to DAQ can be about 92Mbps, which meet the requirements for ETOF upgrading.
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http://arxiv.org/abs/1305.7033
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