Ring Imaging CHerenkov systems based on gaseous photo-detectors: trends and limits around particle accelerators

Since the last RICH Workshop held in 1998, a number of large RICH systems have been built and, some, already operated at different HEP experiments. The main features governing the operation and the performance of these systems are reviewed and discussed in view of possible improvements towards higher rates and ageing performance. As most of the new systems are based on CsI-photocathodes, a review is given on the progress done in the processing of efficient and reproducible large photocathodes. An alternative multi-GEM based photo-detector is discussed.