Status of the PWO crystal production from Russia for CMS-ECAL

After a long period of research and development on PbWO4 and particularly on the improvement of its radiation hardness, the CMS electromagnetic calorimeter (ECAL) has entered its construction phase in September 1998. Before starting the mass production of the PWO crystals, the CMS-ECAL community decided to set up a pre-production in order to define and optimise the process parameters for the production of the 80 000 PbWO4 scintillating crystals needed for the CMS-ECAL. From September 1998 to December 2000, the Bogorodisk Techno-Chemical Plant in Russia has produced 6000 PbW04 (PWO) pre-production crystals and delivered them to CERN where they were fully characterised. The most important results of the pre-production phase were a continuous increase of the yield and a production rate up to 1000 crystals per month, together with a significant improvement and homogenisation of the crystal quality. Taking into account the experience from the pre-production period, by the end of 2000 the BTCP has started the mass production of the PWO crystals for CMS-ECAL. In this paper, an overview on the characteristics of the pre-production crystals will be presented. We will also show the first results on the new development which allow to cut two barrel crystals in a larger ingot.