Clock and trigger distribution for CBM-TOF quality evaluation of RPC super module detector assemblies

Abstract

RPC Super module (SM) detector assemblies are used for charged hadron identification in the Time-of-Flight (TOF) spectrometer at the Compressed Baryonic Matter (CBM) experiment. Each SM contains several multi-gap Resistive Plate Chambers (MRPCs) and provides up to 320 electronic channels in total for high-precision time measurements. Time resolution of the Time-to-Digital Converter (TDC) is required to be better than 20 ps. During mass production, the quality of each SM needs to be evaluated. In order to meet the requirements, the system clock signal as well as the trigger signal should be distributed precisely and synchronously to all electronics modules within the evaluation readout system. In this paper, a hierarchical clock and trigger distribution method is proposed for the quality evaluation of CBM-TOF SM detectors. In a first stage, the master clock and trigger module (CTM) allocated in a 6U PXI chassis distributes the clock and trigger signals to the slave CTM in the same chassis. In a second stage, the slave CTM transmits the clock and trigger signals to the TDC readout module (TRM) through one optical link. In a third stage, the TRM distributes the clock and trigger signals synchronously to 10 individual TDC boards. Laboratory test results show that the clock jitter at the third stage is less than 4 ps (RMS) and the trigger transmission latency from the master CTM to the TDC is about 272 ns with 11 ps (RMS) jitter. The overall performance complies well with the required specifications.