Author: Fartoukh, S.D.
Paper Title Page
MOPPC003 Very Fast LHC Crab Cavity Failures and their Mitigation 121
  • T. Baer, R. Calaga, R. De Maria, S.D. Fartoukh, E. Jensen, R. Tomás, J. Tückmantel, J. Wenninger, B. Yee-Rendon, F. Zimmermann
    CERN, Geneva, Switzerland
  • T. Baer
    University of Hamburg, Hamburg, Germany
  For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is needed to compensate the geometric luminosity loss due to the crossing angle and for luminosity leveling [*]. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a control failure or arcing in the coupler), the voltage and/or phase of a CC can change significantly with a very fast time constant of the order of 1 to 10 LHC turns. This can lead to large, global betatron oscillations of the beam. The impact of CC failures on the beam dynamics is discussed and the results from dedicated simulations are presented. Mitigation strategies to limit the impact of CC failures to an acceptable level are proposed.
* F. Zimmermann and O. Brüning, “Parameter Space for the LHC High-Luminosity Upgrade”, IPAC'12, MOPPC005, May 2012.
MOPPC011 Optics and Layout Solutions for the HL-LHC with Large Aperture Nb3Sn and Nb-Ti Inner Triplets 145
  • S.D. Fartoukh, R. De Maria
    CERN, Geneva, Switzerland
  Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan.
The LHC Upgrade studies, formalized into the High-Luminosity LHC (HL-LHC) project, relies on the feasibility of very low β*, and in particular on a novel achromatic squeezing mechanism, the ATS scheme which is presently under test in the LHC*. We present two optics and layout scenario for the HL-LHC using the ATS scheme, one based on Nb3Sn triplet quadrupoles with a coil aperture compatible with an operational gradient of 150T/m and a backup scenario based on NbTi compatible with an operational gradient of 100T/m. The solution obtained are analyzed in terms of β* reach (flat or round), mechanical acceptance, optics flexibility, chromatic properties, and impact on the dynamic aperture due to the large beta-beating waves induced in the arcs by the ATS scheme.
* S. Fartoukh et al., "The Achromatic Telescopic Squeezing (ATS) scheme: from initial motivations to basic principles, and first demonstration at the LHC," these proceedings.
MOPPC020 Field Tolerances for the Triplet Quadrupoles of the LHC High Luminosity Lattice 169
  • Y. Jiao, Y. Cai, Y. Nosochkov, M.-H. Wang
    SLAC, Menlo Park, California, USA
  • R. De Maria, S.D. Fartoukh, M. Giovannozzi, E. McIntosh
    CERN, Geneva, Switzerland
  Funding: This work is supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
It has been proposed to implement an Achromatic Telescopic Squeezing (ATS) scheme* in the high luminosity LHC lattice to reduce the beta functions at the Interaction Points (IP) up to a factor of 8. As a consequence, the nominal 4.5-km peak beta functions reached in the inner triplets at collision will be increased by the same factor. This therefore justifies the installation of new, larger aperture superconducting triplet quadrupoles. These higher beta functions will enhance the effects of the triplet quadrupole field errors leading to smaller beam dynamic aperture. To maintain the acceptable dynamic aperture, the effects of the triplet multipole field errors must be re-evaluated, thus specifying new tolerances. Such a study has been performed for the so-called “4444” collision optics of the ATS scheme, where the IP beta functions are reduced by a factor of 4 in both planes with respect to a pre-squeezed value of 60 cm at two collision points. The dynamic aperture calculations were performed using SixTrack. The impact on the triplets’ field quality is studied and presented in details.
* S. Fartoukh, “An Achromatic Telescopic Squeezing (ATS) Scheme for LHC Upgrade”, Proc. of IPAC11, p. 2088 (2011).
TUPPC081 First Experimental Observations from the LHC Dynamic Aperture Experiment 1362
  • M. Giovannozzi, M. Albert, G.E. Crockford, S.D. Fartoukh, W. Höfle, E.H. Maclean, A. Macpherson, L. Ponce, S. Redaelli, H. Renshall, F. Roncarolo, R.J. Steinhagen, E. Todesco, R. Tomás, W. Venturini Delsolaro
    CERN, Geneva, Switzerland
  • R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  Following intensive numerical simulations to compute the dynamic aperture for the LHC in the design phase, the successful beam commissioning and the ensuing beam operations opened the possibility of performing beam measurements of the dynamics aperture. In this paper the experimental set-up and the first observations based on the few experimental sessions performed will be presented and discussed in detail.  
TUPPR068 The Achromatic Telescopic Squeezing Scheme: Basic Principles and First Demonstration at the LHC 1978
  • S.D. Fartoukh, R. De Maria, B. Goddard, W. Höfle, M. Lamont, G.J. Müller, L. Ponce, S. Redaelli, R.J. Steinhagen, M. Strzelczyk, R. Tomás, G. Vanbavinckhove, J. Wenninger
    CERN, Geneva, Switzerland
  • R. Miyamoto
    ESS, Lund, Sweden
  The Achromatic Telescopic Squeezing (ATS) scheme [1] is a novel squeezing mechanism enabling the production of very low β* in circular colliders. The basic principles of the ATS scheme will be reviewed together with its strong justification for the High-Luminosity LHC Project. In this context, a few dedicated beam experiments were meticulously prepared and took place at the LHC in 2011. The results obtained will be highlighted, demonstrating already the potential of the ATS scheme for any upgrade project relying on a strong reduction of β*.
[1] S. Fartoukh, "An Achromatic Telescopic Squeezing (ATS) Scheme For The LHC Upgrade," IPAC'11, WEPC037, p. 2088 (2001).