CMS Bulletin

INFRASTRUCTURE

One of the first activities of LS1 has been the refurbishment of the rack ventilation units in the USC55 counting rooms. These rack-mounted turbines have been in service since 2007 and they have largely passed the expected lifetime. Some 450 motor-fans units have been procured in Germany, via the CERN store, and shipped to CMS where a team of technicians has dismounted the old turbines, keeping only the bare chassis, and inserted the new fans. A metallic mesh has also been added to better protect personnel from possible injuries by spinning blades. A full test of several hours has validated the new units, prior to their installation inside the racks. The work, started soon after the beginning of LS1, has been successfully concluded last week.

Figure 1: Drawing of the fan units recently refurbished in the USC55 counting room racks

Image 1: New filter on the main rack water-cooling distribution line

The cooling systems of CMS are gently coming out of their maintenance programme. All water circuits have been put back in operation on 15 June, are in good shape and have no leaks at all, despite the huge interventions completed: full maintenance on the plants – from the towers to the detector circulation systems – cleaning of all filters, installation of an additional filter and the repair of all muon system circuit flow limiters.

The activity still ongoing, guided by the accessibility of the panels, is the replacement of all quick connectors on the radial thermal shields.

Image 2: The TIF CO₂ cooling plant: full-scale prototype for Pixel Phase 1 Upgrade

The fluorocarbon cooling systems serving the Strip Tracker, the Pixel detector and the ECAL Preshower have been completely refurbished to achieve –20 ºC operation and the re-commissioning of the system is reaching its end. By the beginning of July, the full performance tests will have to assess the total power of the system at the lowest design temperatures.

On the surface, the construction of the CO₂ cooling system for Pixel Phase 1 upgrade is completed. All components have been installed and pressure-tested in Building 186 and the first steps towards commissioning are ongoing: I/O verification for the cabling and controls logic verification on a mirror machine, prior to powering of the new plant.