Studies for a fast RICH

We are developing the design of a photon detection system for a fast RICH, to match the requirements arising from the foreseen enlarged luminosity of the COMPASS experiment. The system is based on UV extended multianode photomultipliers and a system of fused silica lenses that collect the light from a larger surface and guide it to the PMT photocathode, preserving the position information. In our design the ratio of the collection and the photosensitive surfaces is larger than in previous applications (it is of the order of 9), to keep the costs of the photon detection system affordable, while the emphasis is on the fast response of the detectors and the associated electronics. We report about the design parameters and the preliminary test beam results.