A highly integrated low-cost readout system for the COMPASS RICH-1 detector

Particle identification at high multiplicities is a key feature of the COMPASS experiment at CERN's SPS. Hadrons up to 50 GeV/c are identified by a RICH detector with a large horizontal and vertical acceptance of plusmn250 mrad and plusmn180 mrad, respectively. The central region of the photon detector is equipped with multi-anode photomultiplier tubes, the remaining 75% of the total active area are covered by MWPCs with Csl photocathodes. In order to improve the performance of the detector at very high beam intensities, more than 62000 channels of a new analog readout system of the MWPCs, based on the APV25 chip, were developed and installed in 2006. The new system features good single photon detection efficiency due to its low noise, negligible dead time at trigger rates up to 50 kHz, and low cost. In addition, sampling of the MWPC signal allows us to measure the signal time with a resolution of about 30 ns or better. The architecture of the new readout system as well as the performance results of the RICH-1 detector in the outer region during 2006 COMPASS run will be discussed.