Machine Protection at the LHC – Experience of Three Years Running and Outlook for Operation at Nominal Energy

With more than 22 fb-1 integrated luminosity delivered to the experiments ATLAS and CMS, the LHC surpassed the results of 2011 by more than a factor 5. This was achieved at 4 TeV, with intensities of ~2e14 p per beam. The uncontrolled loss of only a small fraction of the stored beam is sufficient to damage parts of the superconducting magnet system, accelerator equipment or the particle physics experiments. To protect against such losses, a correct functioning of the complex LHC machine protection (MP) systems through the operational cycle is essential. Operating with up to 140 MJ stored beam energy was only possible due to the experience and confidence gained in the two previous running periods, where the intensity was slowly increased. In this paper the 2012 performance of the MP systems is discussed. The strategy applied for a fast, but safe, intensity ramp up and the monitoring of the MP systems during stable running periods are presented. Weaknesses in the reliability of the MP systems, set-up procedures, and setting adjustments for machine development periods, discovered in 2012, are critically reviewed and improvements for the LHC operation after the up-coming long shut-down (LS1) of the LHC are proposed.