STAR Time of Flight Readout Electronics, DAQ, and Cosmic Ray Test Stand

A novel time-of-flight (TOF) subsystem is under design for the STAR detector at RHIC. A total of 3840 multi-gap resistive plate chambers (MRPC) of 6 pads each are distributed over 120 trays. The total number of channels is 23040. Each TOF tray consists of 192 detector channels and three different types of electronic circuit cards, called "TINO", "TDIG", and "TCPU", listed in order of the data flow. Every 30 trays send their data to a "THUB" card that interfaces to the STAR trigger and transmits the data over a fiber to a fiber receiver which is part of STAR DAQ. The TINO contains the analog front end electronics based on the CERN/LAA NINO custom IC. The output of TINO is passed to the TDIG, where the data are digitized (using the CERN HPTDC ASIC). The TCPU formats and buffers the digital detector information. These formatted data are passed to THUB, which transmits it over an optical fiber to a data receiver in the STAR DAQ room. We have constructed a cosmic ray test system comprised of three plastic scintillators, 4 MRPC modules, and TOF prototype electronics in order to determine the timing resolution expected to be achieved with these electronics in the entire TOF system. Overall timing resolution of 80-110 ps for cosmic ray events has been achieved.