Performance of ACCOS, an Automatic Crystal quality Control System for the PWO crystals of the CMS calorimeter

Nearly 80 000 PWO crystals for the CMS electromagnetic calorimeter will arrive at CERN/Geneva and INFN-ENEA/Rome between now and year 2004. The stringent specifications on their dimensions and optical quality have to be verified prior to their formal acceptation. Automatic systems for measuring the critical parameters of each crystal and recording them in a database have been designed and constructed. The first machine is now in stable operation at CERN. In this note, the performance of each instrument, based on the measurements on ∼1000 pre-production crystals, is analysed in terms of stability and compared to the results of conventional benches.