• K. Hanke, C. Carli, R. Garoby, F. Gerigk, A.M. Lombardi, S. Maury, C. Rossi, M. Vretenar
  CERN, Geneva

The construction of Linac4, a 160 MeV H^- Linac, is the first step in upgrading the LHC injector chain. Unlike CERN's present injector linac, Linac4 will inject into the subsequent synchrotron via charge exchange injection. In a first stage, it will inject into the existing CERN PS Booster. At a later stage, Linac4 has the option to be extended by a superconducting linac (SPL) which could then inject into a new synchrotron (PS2). Construction of Linac4 has started in 2008, and beam operation is presently planned for 2014. An overview of the Linac4 main parameters and design choices is given, and the status of the construction reported.

• O. Piquet, O. Delferrière, M. Desmons, A. France
  CEA, Gif-sur-Yvette
• A.M. Lombardi, C. Rossi, M. Vretenar
  CERN, Geneva

In the Linac 4 and the SPL, a 3 MeV RFQ is required to accelerate the H^- beam from the ion source to the DTL input energy. While the 6-meter long IPHI RFQ was initially chosen for this application, a CERN study* suggested that a dedicated, shorter 3-meter RFQ might present several advantages. The 2D cross-section is optimized for lower power dissipation, while featuring simple geometrical shape suitable for easy machining. RF stability is evaluated using a 4-wire transmission model and 3D simulations, taking electrode modulation into account. The resulting RFQ is intrinsically stable and do not require rod stabilizers. End circuits are tuned with dedicated rods. RF power is fed via a ridged waveguide and a slot iris. Vacuum port assemblies are positioned prior to brazing to minimize RF perturbation. The 32 tuning slugs form a set of stable sampling, able to tune 9 modes. Tuner parameters are derived from bead-pull accuracy specification and fabrication tolerances. Signals delivered by pickup loops inserted in 16 of these tuners will be used to reconstruct the voltage profile under operation. Thermo-mechanical simulations are used to design temperature control specifications.

• 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.