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

Linac4 is a 160 MeV, 40 mA H^- linear accelerator which will be the source of particles for all CERN proton accelerators from 2013. Its construction has started in 2008, as part of a program for the progressive replacement or upgrade of the LHC injectors during the next decade. Linac4 will initially inject into the PS Booster and at a later stage into a 4 GeV Superconducting Proton Linac (SPL), which could ultimately be upgraded to high duty cycle operation. For this reason accelerating structures, rf hardware and shielding of Linac4 are dimensioned for higher duty from the initial phase. Linac4 is normal-conducting, 80 m long and consists of an rf volume ion source, an RFQ, a beam chopping section and a cascade of three different types of 352 MHz accelerating structures. Its main design requirements are high reliability, high beam brightness and low beam loss. The accelerator will be housed in an underground tunnel on the CERN site, which can eventually be extended to the SPL, with equipment installed in a surface building above. The main parameters, the status of the main components, the planning, the project organisation and the civil engineering infrastructure are presented.

• C. Rossi, P. Bourquin, J.-B. Lallement, A.M. Lombardi, S.J. Mathot, M.A. Timmins, G. Vandoni, M. Vretenar
  CERN, Geneva
• S. Cazaux, O. Delferrière, M. Desmons, R.D. Duperrier, A. France, D. Leboeuf, O. Piquet
  CEA, Gif-sur-Yvette

The first stage of acceleration in Linac4, the new 160 MeV CERN H^- injector, is a 352 MHz, 3 m long Radiofrequency Quadrupole (RFQ) Accelerator. The RFQ will capture a 70 mA, 45 keV beam from the rf source and accelerate it to 3 MeV, an energy suitable for chopping and injecting the beam in a conventional Drift Tube Linac. Although the RFQ will be initially operated at low duty cycle (0.1%), its design is compatible with higher duty cycle (10%) as the front-end for a possible high-intensity upgrade of the CERN linac facility. The RFQ will be of the brazed-copper design and will be built and assembled at CERN. Beam dynamics design allows for a compact structure made of a single resonant unit. Field symmetry is ensured by fixed tuners placed along the structure. In this paper we present the rf and mechanical design, the beam dynamics and the sensitivity to fabrication and to rf errors.

• R. Garoby, O. Brunner, S. Calatroni, E. Ciapala, F. Gerigk, A.M. Lombardi, R. Losito, V. Parma, C. Rossi, J. Tuckmantel, M. Vretenar, W. Weingarten
  CERN, Geneva

As part of the upgrade of the LHC injector complex at CERN, the construction of a 4 GeV Superconducting Proton Linac (the SPL, in fact an H^- accelerator) is planned to begin in 2012. Depending upon physics requests, it should be upgradeable to 5 GeV and multi-MW beam power at a later stage. The construction of Linac4, its low energy front end, has started at the beginning of 2008. A full project proposal with a cost estimate for the low power version of the SPL aimed at improving LHC performance has to be ready for mid-2011. As a first step towards that goal, essential machine parameters like rf frequency, cooling temperature and beam current have recently been revisited and plans have been drawn for designing and testing critical components. The SPL parameters are reviewed in the context of the CERN plans for upgrading the LHC injectors, and the foreseen developments during the next years are described.

• P. Shrivastava, J. Mulchandani, V.C. Sahni
  RRCAT, Indore (M.P.)
• F. Bordry, C. De Almeida Martins, C. Rossi
  CERN, Geneva

Funding: Department of Atomic Energy, India.
CERN is building a 352.2 MHz, 3 MeV RFQ based Test Stand as first part of LINAC 4. Extending its collaboration with DAE of India, CERN approached us to design and develop a high voltage pulsed modulator for 1 MW LEP klystrons (planning their reuse). Three design schemes were proposed out of which an all solid state bouncer compensated modulator was chosen for follow up development. The main features of the modulator are: no gas tube crow-bar, all solid state construction low rise/fall times and high stability of the flat top. The major specifications are output voltage upto 110 kV, output current upto 24 Amp, pulse duration 800 μs, PRR 2Hz, pulse droop <1% and ripple on pulse top <0.1%. The energy in klystron arc is restricted to 10J. Based on these principles, a modulator has been developed and constructed at CERN and is currently undergoing tests with a klystron while another one with similar development is in the final stages of integration/evaluation at RRCAT. The present paper describes the topology, simulation results, protection strategy and integration aspects of the pulse modulator and would briefly summarize the results.

The work is done under DAE CERN Collaboration under NAT Protocol.