Fast Photon Detection for Particle Identification with COMPASS RICH 1
Particle identification at high rates is an important challenge for many current and future high energy physics experiments. The upgrade of the COMPASS RICH 1 detector requires a new technique for Cherenkov photon detection at count rates of several $10^6$ per channel in the central detector region, and a read out system allowing for trigger rates of up to 100 kHz. To cope with these requirements, the photon detectors in the central region have been replaced with the detection system described in this paper. In the peripheral regions, the existing multi wire proportional chambers with CsI photocathode are now read out via a new system employing APV pre amplifiers and flash ADC chips. The new detection system consists of multi anode photomultiplier tubes (MAPMT) and fast read out electronics based on the MAD4 discriminator and the F1 TDC chip. The RICH 1 is in operation in its upgraded version for the 2006 CERN SPS run. We present the photon detection design, constructive aspects and the first Cherenkov light in the detector.