Investigations of rate and multi-hit capability of multi-gap resistive plate chambers

The application of multi-gap resistive plate chambers (MRPC) for time-of-flight (TOF) measurements in future high-rate heavy-ion-collision experiments like CBM (Compressed Baryonic Matter) at FAIR is constrained by both challenging particle-flux and multi-hit conditions on the counter surface. Towards the center of the 120 m${}^2$ TOF wall of CBM, fluxes of up to 25 kHz/cm${}^2$ in gold-on-gold collisions at 10 MHz and 11 A GeV (SIS100) are handled by detectors with special low-resistive glass. At the periphery, common-glass counters are used for cost reasons. In this work, test-beam results for corresponding prototypes obtained in a multi-hit environment under moderate particle fluxes of 1–2 kHz/cm${}^2$ at CERN/SPS are systematically analyzed for rate and interference effects on counter performance. For a reproduction in simulations, a novel parametrization of the MRPC response function is introduced which models both the impact of sustained irradiation on detection capability in time and the distortion of reconstructed hits by interfering induced signals. An envisaged qualitative agreement is achieved between real and simulated observations. While only the common-glass counter shows an expected performance degradation due to rate, the response evaluation of both prototypes via correlations on adjacent detectors is significantly complicated by multi-hit effects. The new response model provides a reliable simulation reference for further investigations on this matter.