Performance of the BIS78 RPC detectors: a new concept of electronics and detector integration for high-rate and fast timing large size RPCs

The reduction of the average charge per count in the gas along with the capability to discriminate very small signals from noise can allow an efficient and long-term Resistive Plate Chamber detector operation in high radiation background environment. This goal has been reached during the R&D program of the BIS78 upgrade project of the ATLAS detector at LHC through the deep integration of a fast (100 ps peaking time) and sensitive (as small as 100 μV threshold) Front-End electronics (FE) with a very large size detector structure. This innovative RPC integration concept pivots on a newly conceived faraday cage, embedding the readout strips and the FE, tightly wrapped around a 1 mm gas gap RPC with 1.2 mm thick electrodes, as a fully independent singlet structure. We studied the performance of BIS78 production triplet chambers, made of 3 independent singlets of 2 m2, each providing a 2D space and time information, showing a minimum threshold achievable of 3 pC of average charge per count produced inside the gas gap. We show that these chambers grant a record combined performance of better than 95% single gap efficiency, time resolution of 350 ps and 10 kHz/cm2 rate capability.