The optical systems of LHCb RICHes : a study on the mirror walls and mirrors specifications

The LHCb detector is being developed and constructed for the LHC project at CERN. For its particle identification sub-detectors, it features two Ring Imaging CHerenkov detectors. Major components are their mirrors together with all the required structures to achieve proper alignment and optical resolution. In the following, we describe in short the optical systems of both RICHes and the procedures for their survey and alignment. Then, we discuss what are the major considerations for the mirror choice. Their specifications are given together with the results achieved on several prototypes through a collaboration program with industry. Finally, the experimental set-ups developed and realized to precisely characterize mirrors optical properties are described in detail. These will serve for the final mirror qualification.