Crystal Properties in the Electromagnetic Calorimeter of CMS

The CompactMuon Solenoid (CMS) is a multi-purpose detector for LHC. The electromagnetic calorimeter (ECAL) contains 75848 lead tungstate crystals allowing a very accurate energy measurement of electrons and photons in the GeV - TeV energy range. More than two thirds of the ECAL Barrel has been already assembled. In this paper an updated analysis on the optical and scintillation properties of about 50000 crystals and an overview on the construction status of the calorimeter are presented. Furthermore the use of crystal production measurements for the calorimeter precalibration is discussed.