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The 350 MJ stored energy of the 7 TeV LHC beams can seriously damage the beam line elements in case of accidental beam losses. Notably, the LHC collimators, which sit at 6 to 7 σs from the beam centre (1.2-1.4 mm), might be hit and possibly damaged in case of failures, with a consequent degradation of their cleaning performance. The experience from operating machines shows that an a-posteriori identification of the damaged collimators from the observed performance degradation is extremely challenging. Collimator tests with beam at the SPS have proven that the impact of 450 GeV proton beams at intensities from 1010 to 3x1013 can be detected by measuring the collimator vibrations. This was achieved by using high-resolution, radiation hard accelerometers and a microphone to record mechanical and sound vibrations of a LHC-like prototype collimator with impacting beams at different intensities and depth. A similar system could be also used in the LHC to detect collimators damaged by the beam.
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- R.W. Assmann, O. Aberle, G. Arduini, A. Bertarelli, H.-H. Braun, M. Brugger, H. Burkhardt, S. Calatroni, F. Caspers, E. Chiaveri, A. Dallocchio, B. Dehning, A. Ferrari, M. Gasior, A. Grudiev, E.B. Holzer, J.-B. Jeanneret, J.M. Jimenez, Y. Kadi, R. Losito, M. Magistris, A.M. Masi, M. Mayer, E. Métral, R. Perret, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, M. Santana-Leitner, D. Schulte, P. Sievers, E. Tsoulou, H. Vincke, V. Vlachoudis, J. Wenninger
CERN, Geneva
- I. Baishev, I.L. Kurochkin
IHEP Protvino, Protvino, Moscow Region
- G. Spiezia
Naples University Federico II, Science and Technology Pole, Napoli
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The problem of collimation and beam cleaning concerns one of the most challenging aspects of the LHC project. A collimation system must be designed, built, installed and commissioned with parameters that extend the present state-of-the-art by 2-3 orders of magnitude. Problems include robustness, cleaning efficiency, impedance and operational aspects. A strong design effort has been performed at CERN over the last two years. The system design has now been finalized for the two cleaning insertions. The adopted phased approach is described and the expected collimation performance is discussed. In parallel robust and precisely controllable collimators have been designed. Several LHC prototype collimators have been built and tested with the highest beam intensities that are presently available at CERN. The successful beam tests are presented, including beam-based setup procedures, a 2 MJ robustness test and measurements of the collimator-induced impedance. Finally, an outlook is presented on the challenges that are ahead in the coming years.
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