Author: Baer, T.
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.
 
 
TUPPR092 Transient Beam Losses in the LHC Injection Kickers from Micron Scale Dust Particles 2044
 
  • B. Goddard, P. Adraktas, T. Baer, M.J. Barnes, F. Cerutti, A. Ferrari, N. Garrel, A.H.J. Gerardin, M. Guinchard, A. Lechner, A. Masi, V. Mertens, R. Morón Ballester, S. Redaelli, J.A. Uythoven, V. Vlachoudis, F. Zimmermann
    CERN, Geneva, Switzerland
 
  Transient beam losses on a time scale of a few ms have been observed in the LHC injection kickers, occurring mainly shortly after beam injection with a strong correlation in time to the kicker pulsing. The beam losses, which have at times affected LHC availability, are attributed to micron scale ceramic dust particles detached from the alumina beam pipe and accelerated into the beam. The beam related observations are described, together with laboratory measurements of beam pipe contamination and kicker vibration, simulations of electric field in the beam pipe and the basic dynamic model. Energy deposition simulations modelling the beam losses are presented and compared to measurement. Extrapolations to future LHC operation at higher intensities and energies are made, and prospects for mitigation are discussed.  
 
THPPP010 LHC Orbit Correction Reproducibility and Related Machine Protection 3746
 
  • K. Fuchsberger, T. Baer, R. Schmidt, J. Wenninger
    CERN, Geneva, Switzerland
 
  The Large Hadron Collider (LHC) has an unprecedented nominal stored beam energy of up to 362 MJ per beam. In order to ensure an adequate machine protection by the collimation system, a high reproducibility of the beam position at collimators and special elements like the final focus quadrupoles is essential. This is realized by a combination of manual orbit corrections, feed forward and real time feedback. In order to protect the LHC against inconsistent orbit corrections, which could put the machine in a vulnerable state, a novel software-based interlock system for orbit corrector currents was developed. In this paper, the principle of the new interlock system is described and the reproducibility of the LHC orbit correction is discussed against the background of this system.  
 
THPPP086 UFOs in the LHC: Observations, Studies and Extrapolations 3936
 
  • T. Baer, M.J. Barnes, F. Cerutti, A. Ferrari, N. Garrel, B. Goddard, E.B. Holzer, S. Jackson, A. Lechner, V. Mertens, M. Misiowiec, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, V. Vlachoudis, J. Wenninger, C. Zamantzas, F. Zimmermann
    CERN, Geneva, Switzerland
  • T. Baer
    University of Hamburg, Hamburg, Germany
  • N. Fuster Martinez
    Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
 
  Unidentified falling objects (UFOs) are potentially a major luminosity limitation for nominal LHC operation. They are presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam. With large-scale increases and optimizations of the beam loss monitor (BLM) thresholds, their impact on LHC availability was mitigated from mid 2011 onwards. For higher beam energy and lower magnet quench limits, the problem is expected to be considerably worse, though. In 2011/12, the diagnostics for UFO events were significantly improved: dedicated experiments and measurements in the LHC and in the laboratory were made and complemented by FLUKA simulations and theoretical studies. The state of knowledge, extrapolations for nominal LHC operation and mitigation strategies are presented.  
 
THPPP086 UFOs in the LHC: Observations, Studies and Extrapolations 3936
 
  • T. Baer, M.J. Barnes, F. Cerutti, A. Ferrari, N. Garrel, B. Goddard, E.B. Holzer, S. Jackson, A. Lechner, V. Mertens, M. Misiowiec, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, V. Vlachoudis, J. Wenninger, C. Zamantzas, F. Zimmermann
    CERN, Geneva, Switzerland
  • T. Baer
    University of Hamburg, Hamburg, Germany
  • N. Fuster Martinez
    Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
 
  Unidentified falling objects (UFOs) are potentially a major luminosity limitation for nominal LHC operation. They are presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam. With large-scale increases and optimizations of the beam loss monitor (BLM) thresholds, their impact on LHC availability was mitigated from mid 2011 onwards. For higher beam energy and lower magnet quench limits, the problem is expected to be considerably worse, though. In 2011/12, the diagnostics for UFO events were significantly improved: dedicated experiments and measurements in the LHC and in the laboratory were made and complemented by FLUKA simulations and theoretical studies. The state of knowledge, extrapolations for nominal LHC operation and mitigation strategies are presented.