• B. Mikulec, G. Bellodi, K. Hanke, T. Hermanns
  CERN, Geneva
• M. Eshraqi
  ESS, Lund

Linac4 will be the new linear accelerator of the CERN accelerator chain delivering H^- ions at 160 MeV from 2016. The increased injection energy compared to the 50 MeV of its predecessor Linac2, combined with a H^- charge-exchange injection, will pave the way to reach ultimate goals for the LHC luminosity. Extensive commissioning for Linac4 is planned for the coming years. For this purpose, the beam will be studied after the exit of Linac4 in a straight line ending at the Linac4 dump, equipped with various beam instruments. An almost 180 m long transfer line will guide the beam to the charge exchange injection point at the entry of the Proton Synchrotron Booster. About 50 m upstream of this point, two measurement lines will be upgraded to perform transverse emittance measurements as well as energy and energy spread measurements of the Linac4 beam. A detailed description of the beam measurement principles and setups at these three Linac4 diagnostics lines related to distinct Linac4 commissioning phases will be given.

• G. Bellodi, M. Eshraqi, M.G. Garcia Tudela, L.M. Hein, J.-B. Lallement, A.M. Lombardi, P.A. Posocco, E. Sargsyan
  CERN, Geneva
• J. Stovall
  TechSource, Santa Fe, New Mexico

Linac4 is a new 160 MeV, 40 mA average beam current H^- accelerator which will be the source of particles for all proton accelerators at CERN as from 2015. Construction started in October 2008, and beam commissioning of the 3MeV frontend is scheduled for early next year. A baseline design of the linac beam dynamics was completed 2 years ago and validated by a systematic campaign of transverse and longitudinal error studies to assess tolerance limits and machine activation levels. Recent studies have been mainly focused on optimising this design to achieve both a smoother performance for nominal beam conditions and to gain operational flexibility for non-nominal scenarios. These include a review of the chopper beam dynamics design, a re-definition of the DTL and CCDTL inter-tank regions and a study of operational schemes for reduced beam currents (either permanent or in pulse-to-pulse mode). These studies have been carried out in parallel to first specifications for a beam commissioning strategy of the linac and its low-energy front-end.

• F. Roncarolo, G. Bellodi, E. Bravin, B. Dehning, M. Duraffourg, G.J. Focker, D. Gerard, E.B. Holzer, LF. Lenardon, U. Raich, L. Søby, M. Sordet, J. Tan, G. Tranquille, VC. Vuitton, C. Zamantzas
  CERN, Geneva
• B. Cheymol
  Université Blaise Pascal, Clermont-Ferrand

The CERN LINAC4 will represent the first upgrade of the LHC injection chain, by accelerating H^- ions from 45 KeV to 160 MeV for charge-exchange injection into the PS Booster. In order to provide its safe and efficient commissioning and operation, a wide variety of beam diagnostics devices has been designed for installation at convenient locations all over the accelerator length and in the transfer line to the PS Booster. This paper gives an overview of all instrumentation devices, including those to measure beam position, transverse and longitudinal profile, beam current and beam loss. The well advanced status of the system design and the main instrument features are discussed.