The ring imaging Cherenkov detectors of DELPHI

A ring imaging Cherenkov (RICH) detector system has been built and is now in full operation within the DELPHI experiment. Large data samples of Z/sup 0/ decays are being collected with good resolution on the observed Cherenkov angles. Several studies of Z/sup 0/ decays using the RICH have already been performed on limited samples. Disturbance of the detector operation caused by shrinkage of polymeric construction materials and by migration of radiator substance is reported. These effects have been counteracted and do not endanger the quality of the data. >