The Compact Muon Solenoid (CMS) experiment is a general purpose detector being operated at Large Hadron Collider (LHC) facility at CERN. The RE4 upgrade project was envisaged to improve the Level-1 trigger efficiency in the forward region, when LHC would run at its full designed energy and luminosity after the first Long Shutdown (LS-1, 2013-2014). About 200 RPCs were built for the upgrade at three assembly sites in India, CERN and Ghent. India contributed to 50, RE4/2 RPCs along with 200 Cu-cooling units for the entire upgrade for which the assembly and characterization of RPCs was carried out jointly by Nuclear Physics Division-BARC and Panjab University-Chandigarh. The gas-gaps after their arrival from KODEL, South Korea, underwent mechanical tests for leak and popped spacers, followed by electrical tests for long term monitoring of leakage currents. After the assembly, each RPC was evaluated for its efficiency, cluster size, noise and strip profiles. The Cu-cooling units build at BARC were also tested according to the quality control protocols for any leakage. All the relevant data was uploaded onto the CMS-RPC data base prior to dispatch of RPCs to CERN. At CERN, the RE4/2 type and RE4/3 type RPCs were assembled to a Super Module (SM), which was further tested for the leaks in the Cu-cooling systems. The SMs were then transported to Point 5 and both the End Caps (± RE4) were successfully installed and commissioned in the summer of 2014.
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