• L. Bottura, M.C.L. Buzio, N. Catalan-Lasheras, L. Deniau, M. DiCastro, S.D. Fartoukh, M. Giovannozzi, P. Hagen, J.-P. Koutchouk, M. Lamont, J. Miles, RV. Remondino, N.J. Sammut, S. Sanfilippo, F. Schmidt, D. Sernelius, R.J. Steinhagen, M. Strzelczyk, E. Todesco, R. Tomás, W. Venturini Delsolaro, L. Walckiers, J. Wenninger, R. Wolf, P. Xydi
  CERN, Geneva

The start-up of the LHC has provided the first field test for the concept, functionality and accuracy of FiDeL, the Field Description for the LHC. FiDeL is primarily a parametric model of the transfer function of the main field integrals generated by the series of magnets in the LHC powering circuits, from main optical elements to high-order harmonic correctors, both superconducting and normal-conducting magnets. In addition, the same framework is used to predict harmonic errors of both static and dynamic nature, and forecast appropriate corrections. In this paper we give a description of the level of detail achieved in the model and the rationale adopted for the LHC start-up. Beam-based measurements have been used for an assessment of the first-shot accuracy in the prediction of the current setting for the main arc magnets*.

*The work reported has been performed by the authors and the FiDeL Team

• S. Redaelli, I.V. Agapov, B. Dehning, M. Giovannozzi, F. Roncarolo, R. Tomás
  CERN, Geneva
• R. Calaga
  BNL, Upton, Long Island, New York

Various LHC injection tests were performed in August and early September 2008 in preparation for the circulating beam operation. These tests provided the first opportunity to measure with beam the available mechanical aperture in two LHC sectors (2-3 and 7-8). The aperture was probed by exciting free oscillations and local orbit bumps of the injected beam trajectories. Intensities of a few 10⁹ protons were used to remain safely below the quench limit of superconducting magnets in case of beam losses. In this paper the methods used to measure the mechanical aperture, the available on-line tools, and beam measurements for both sectors are presented. Detailed comparisons with the expected results from the as-built aperture models are also presented. It is shown that the measurements results are in good agreement with the LHC design aperture.

• R. Tomás, M. Aiba, S.D. Fartoukh, F. Franchi, M. Giovannozzi, V. Kain, M. Lamont, G. Vanbavinckhove, J. Wenninger, F. Zimmermann
  CERN, Geneva
• R. Calaga
  BNL, Upton, Long Island, New York
• A. Morita
  KEK, Ibaraki

In 2008 beam successfully circulated in the LHC. Thanks to an excellent functioning of the BPM system and the related software, injection oscillations were recorded for the first 90 turns at all BPMs. The analysis of these data gives the unique opportunity of evaluating the periodic optics and inferring possible error sources.

• F. Zimmermann, S.D. Fartoukh, M. Giovannozzi, V. Kain, M. Lamont, Y. Sun, R. Tomás
  CERN, Geneva
• R. Calaga
  BNL, Upton, Long Island, New York

In early LHC commissioning, linear and "higher-order" polarity checks were performed for one octant per beam, by launching suitable free betatron oscillations and then inverting a magnet-circuit polarity or strength. Circuits tested included trim quadrupoles, skew quadrupoles, lattice sextupoles, sextupole spool-pieces, Landau octupoles, and skew sextupoles. A nonzero momentum offset was introduced to enhance the measurement quality. The low-intensity single-pass measurements proved sufficiently sensitive to verify the polarity and the amplitude of (almost) all circuits under investigation, as well as the alignment of individual trim quadrupoles. A systematic polarity inversion detected by this measurement helped to pin down the origin of observed dispersion errors. Later, the periodic "ring dispersion" was reconstructed from the full first-turn trajectory of an injected off-momentum beam, by removing, at each location, the large incoming dispersion mismatch, forward-propagated via the optics model. Various combinations of inverted trim quadrupoles were considered in this model until reaching a good agreement of reconstructed dispersion and prediction.

• S.S. Gilardoni, F. Arnold Malandain, E. Benedetto, T. Bohl, S. Cettour Cave, K. Cornelis, H. Damerau, F. Follin, T. Fowler, F. Franchi, P. Freyermuth, H. Genoud, R. Giachino, M. Giovannozzi, S. Hancock, Y. Le Borgne, D. Manglunki, G. Metral, L. Pereira, J.P. Ridewood, Y. Riva, M. Schokker, L. Sermeus, R.R. Steerenberg, B. Vandorpe, J. Wenninger
  CERN, Geneva

The Multi-Turn Extraction, a new type of extraction based on beam trapping inside stable islands in the horizontal phase space, has been commissioned during the 2008 run of the CERN Proton Synchrotron. Both single- and multi-bunch beams with a total intensity up to 1.4×10¹³ protons have been extracted with efficiencies up to 98%. Furthermore, injection tests in the CERN Super Proton Synchrotron were performed, with the beam then accelerated and extracted to produce neutrinos for the CERN Neutrino to Gran Sasso experiments. The results of the extensive measurement campaign are presented and discussed in details.

• S.S. Gilardoni, D. Allard, M.J. Barnes, O.E. Berrig, A. Beuret, D. Bodart, P. Bourquin, R. Brown, M. Caccioppoli, F. Caspers, J.-M. Cravero, C.G.A. Dehavay, T. Dobers, M. Dupont, G. Favre, T. Fowler, F. Franchi, M. Giovannozzi, J. Hansen, M. Karppinen, C. Lacroix, E. Mahner, V. Mertens, J. Monteiro, R. Noulibos, E. Page, R. Principe, C. Rossi, L. Sermeus, R.R. Steerenberg, G. Vandoni, G. Villiger, Th. Zickler, C. de Almeida Martins
  CERN, Geneva

The implementation of new Multi-turn extraction at the CERN Proton Synchrotron required major hardware changes for the nearly 50-year old accelerator. The installation of new PFNs and refurbished kicker magnets for the extraction, new sextupole and octupole magnets, new power converters, together with an in-depth review of the machine aperture leading to the design of new vacuum chambers was required. As a result, a heavy programme of interventions had to be scheduled during the winter shut-down 2007-8. The newly installed hardware and its commissioning is presented and discussed in details.

• F. Zimmermann, R.W. Assmann, M. Giovannozzi, Y. Papaphilippou
  CERN, Geneva
• A. Caldwell, G.X. Xia
  MPI-P, München

Short high-energy proton bunches have been proposed as efficient drivers for future single-stage electron-beam plasma accelerators. We discuss if and how the desired proton bunches could be obtained in the CERN accelerator complex, considering various compression schemes, such as a fast non-adiabatic lattice change prior to extraction from a storage ring or the use of transversely deflecting cavities.