Multi-strip MRPCs for FOPI

During the last years FOPI has developed a new ToF system as an upgrade of the existing detector based on Multi-strip Multi-gap Resistive Plate Chambers (MMRPCs). The intention is to increase the charged Kaon identification up to a laboratory momentum of 1GeV/c and to enhance the azimuthal detector granularity. The new ToF barrel has an active area of 5m2 with 2400 individual strips (900×1.6mm2) [A. Schüttauf, et al., Nucl. Phys. B 158 (2006) 52] which are read out on both sides by a custom designed electronics [M. Ciobanu, et al., IEEE Trans. Nucl. Sci. NS-54 (4) (2007) 1201; K. Koch, et al., IEEE Trans. Nucl. Sci. NS-52(3) (2005) 745]. To reach the envisaged goal a time resolution of 100ps is needed, at a flight path of 1–1.3m. Due to the rare production of the K− at SIS energies the efficiency of the MMRPCs has to be above 95%. We report on measurements with the detectors and electronics from the mass production line. For this purpose we used a proton beam at 2.0 and 1.25GeV, at rates between 0.1 and 5kHz/cm2 to determine the timing, efficiency and rate capability of the MMRPCs.