Vacuum performance and lessons for 2012

During the LHC run 2011, a tremendous progress has been made towards the machine operation with design parameters. In the same time, the run confirmed the sensitivity of the beam vacuum system to the machine parameters. As expected, a successful scrubbing period allowed mitigating the effects of the electron cloud giving room to an entire filling of the ring with 50 ns beams. In parallel issues such as the impact of the beam screen regulation, pressures spikes and local outgassing were observed during the year. On-line mitigations and immediate compensatory measures implemented during the winter technical stop are reviewed together with their efficiencies. The expected limitations while waiting for LS1 consolidation or when running with 25 ns beams are addressed. Lessons for 2012 are discussed