Design and performance of the cooling system for the electromagnetic calorimeter of CMS

For the physics program of the CMS experiment at the LHC to be carried out successfully, excellent electromagnetic calorimetry is required. Given the thermal properties of CMS ECAL, keeping the constant term of the energy resolution below 0.5% needs its temperature to be stabilized at 18/spl deg/C within 0.05/spl deg/C. A prototype module of ECAL with the final cooling system has been tested at CERN to check its integration with the read-out electronics and verify that it complies with the severe thermal requirements. The thermal performance of the cooling system is reported here.