• F.F. Bertinelli, N. Catalan-Lasheras, P. Fessia, C. Garion, S.J. Mathot, A. Perin, C.E. Scheuerlein, S. Sgobba, H.H.J. Ten Kate, J.Ph. G. L. Tock, A.P. Verweij, G.P. Willering
  CERN, Geneva

Following the analysis of the September 2008 LHC incident, the assembly process and the quality assurance of the main 13 kA interconnection splices were improved, with new measurement and diagnostics methods introduced. During the 2008-2009 shutdown ~5% of these 10 000 splices were newly assembled with these improvements implemented, but essentially maintaining the original design. It is known today that a limiting factor towards 7 TeV operation is the normal conducting resistance of ~15% of the original main 13 kA interconnection splices, associated to the electrical continuity of the copper stabiliser. A "Splices Task Force" has been set up at CERN to evaluate the need for, develop and test design improvements and prepare the implementation of a consolidation campaign. Important issues of splice design, process choice, resources and time requirements are considered.

• S.J. Mathot, P. Bourquin, A. Briswalter, Th. Callamand, J. Carosone, N. Favre, J.-M. Geisser, A.M. Lombardi, V. Maire, M. Malabaila, D. Pugnat, Ph. Richerot, B. Riffaud, C. Rossi, M.A. Timmins, A. Vacca, G. Vandoni, M. Vretenar
  CERN, Geneva

The Linac4 RFQ will accelerate the H^- beam from the ion source to the energy of 3 MeV. The RFQ is composed of three sections of 1 meter each, assembled by means of ultra high vacuum flanges and an adjustable centering ring. The complete 3-m long RFQ will be supported isostatically over 3 points like a simple beam in order to minimise the maximum deflection. The ridge line, used to feed the RF power into the RFQ, will be supported via springs and its position adjusted in such way that no strain is introduced into the RFQ at the moment of its connection. The mechanical design has been done at CERN where the modules are completely manufactured, heat treated and brazed also. In that way, all of the processes are carefully controlled and the influence, notably of the heat treatments, has been understood in a better way. Since 2002 several four vanes RFQ modules have been brazed at CERN for the TRASCO and IPHI projects. A two-step brazing procedure has been tested. This technique is actually used for the assembly of the CERN Linac4 RFQ. This paper describes the design, the mechanical procedures adopted for machining and assembly and the first results obtained.

• D. Wollmann, O. Aberle, G. Arnau-Izquierdo, R.W. Assmann, J.-P. Bacher, V. Baglin, G. Bellodi, A. Bertarelli, A.P. Bouzoud, C. Bracco, R. Bruce, M. Brugger, S. Calatroni, F. Caspers, F. Cerutti, R. Chamizo, A. Cherif, E. Chiaveri, P. Chiggiato, A. Dallocchio, R. De Morais Amaral, B. Dehning, M. Donze, A. Ferrari, R. Folch, P. Francon, P. Gander, J.-M. Geisser, A. Grudiev, E.B. Holzer, D. Jacquet, J.B. Jeanneret, J.M. Jimenez, M. Jonker, J.M. Jowett, Y. Kadi, K. Kershaw, L. Lari, J. Lendaro, F. Loprete, R. Losito, M. Magistris, M. Malabaila, A. Marsili, A. Masi, S.J. Mathot, M. Mayer, C.C. Mitifiot, N. Mounet, E. Métral, A. Nordt, R. Perret, S. Perrollaz, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, A. Rossi, B. Salvant, M. Santana-Leitner, I. Sexton, P. Sievers, T. Tardy, M.A. Timmins, E. Tsoulou, E. Veyrunes, H. Vincke, V. Vlachoudis, V. Vuillemin, Th. Weiler, F. Zimmermann
  CERN, Geneva
• I. Baishev, I.A. Kurochkin
  IHEP Protvino, Protvino, Moscow Region
• D. Kaltchev
  TRIUMF, Vancouver

The LHC has two dedicated cleaning insertions: IR3 for momentum cleaning and IR7 for betatron cleaning. The collimation system has been specified and built with tight mechanical tolerances (e.g. jaw flatness ~ 40 μm) and is designed to achieve a high accuracy and reproducibility of the jaw positions. The practically achievable cleaning efficiency of the present Phase-I system depends on the precision of the jaw centering around the beam, the accuracy of the gap size and the jaw parallelism against the beam. The reproducibility and stability of the system is important to avoid the frequent repetition of beam based alignment which is currently a lengthy procedure. Within this paper we describe the method used for the beam based alignment of the LHC collimation system, its achieved accuracy and stability and its performance at 450GeV.

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