The compact muon solenoid RPC barrel detector

Resistive Plate Chambers (RPC) have been chosen as dedicated trigger muon detectors for the Compact Muon Solenoid[CMS collaboration, Technical Design Report, CERN/LHCC 94-38, 1994. [1]] experiment at the Large Hadron Collider[The LHC project at CERN, LHC-project-report-36, 1996. [2]] at CERN. Four Italian groups from Bari, Frascati, Napoli and Pavia and two Bulgariangroups from Sofia have participated in designing and constructing the RPC barrel system. A sophisticated and complex production line has been organized by the collaboration to build the 480 RPC chambers, with a quality assurance (QA) test, made by 3 consecutive steps, in order to assure full functionality of the chambers. A final certification of the chambers has been made at ISR (CERN) with a month-long test. After that the RPCs have been coupled to the Drift Tube chamber and installed in the iron return yokeof the CMS solenoid. The first chamber was produced in 2002 and last was installed in October 2007. The system is now completely installed and commissioning has been going on since the second half of 2005 to complete the Large Hadron Collider(LHC) startup in the summer of 2008. The chamber construction, the test made, the main results achieved and a short description of all the services needed to run the RPC barrel system will be described in this paper.