Development of high-rate MRPCs for high resolution time-of-flight systems

We show how the high charged-particle fluxes (1-20 kHz/cm²) expected over the 150 m² large time-of-flight wall of the future Compressed Baryonic Matter experiment (CBM) at FAIR can be realistically handled with Multi-gap Resistive Plate Chambers (MRPCs). This crucial 100-fold increase of the chamber rate capability, as compared to that of standard MRPCs presently employed in experiments resorting to sub-100 ps timing, has been achieved thanks to the development of a new type of low-resistive doped glass. Following the encouraging results previously obtained with small counters, two types of modules (active area: ~150 cm²) have been built at Tsinghua University with the new material. The measurements conveyed in this work, obtained with a quasi-minimum ionizing electron beam, prove their suitability as the building blocks of the present hadron-identification concept of the CBM experiment. Namely, they provide a time resolution better than 80 ps and an efficiency above 90% at particle fluxes of 50 kHz/cm², being at the core of a modular concept that is easily scalable. Recent measurements of the electrical and mechanical properties of this new material, together with its long-term behavior, are shortly summarized.