Operational experience with the 4π ring imaging Cherenkov detector of DELPHI

The ring imaging Cherenkov detector in the DELPHI Experiment at LEP allows hadron identification over a momentum range up to about 40 Gev/c over a near to 4π solid angle. Photons emitted by charged particles traversing gas and liquid radiators which are filled with UV-transparent perfluorocarbons, are used for Cherenkov angle reconstruction. Stable operation ensures that the detector is an efficient and powerful instrument. Monitoring of the detector parameters is of utmost importance to achieve good data quality and adequate data processing. The hadron identifying power of the ring imaging Cherenkov detector closely meets the main design values. Computerized control and monitoring features of the different subsystems will be presented. The interplay between detector parameters and the particle separating capacity of the detector will be discussed.