Author: Uythoven, J.A.
Paper Title Page
TUPC137 UFOs in the LHC 1347
 
  • T. Baer, M.J. Barnes, B. Goddard, E.B. Holzer, J.M. Jimenez, A. Lechner, V. Mertens, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, B. Velghe, J. Wenninger, F. Zimmermann
    CERN, Geneva, Switzerland
 
  One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (”Unidentified Falling Objects”). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns when they interact with the beam. In 2011, the diagnostics for such events was significantly improved which allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge and mitigation strategies are presented.  
 
TUPZ016 First Run of the LHC as a Heavy-ion Collider 1837
 
  • J.M. Jowett, G. Arduini, R.W. Assmann, P. Baudrenghien, C. Carli, M. Lamont, M. Solfaroli Camillocci, J.A. Uythoven, W. Venturini Delsolaro, J. Wenninger
    CERN, Geneva, Switzerland
 
  A year of LHC operation typically consists of an extended run with colliding protons, ending with a month in which the LHC has to switch to its second role as a heavy ion collider and provide a useful integrated luminosity to three experiments. The first such run in November 2010 demonstrated that this is feasible. Commissioning was extremely rapid, with collisions of Pb nuclei achieved within 55 h of first injection. Stable beams for physics data-taking were declared a little over one day later and the final integrated luminosity substantially exceeded expectations.  
 
WEPC174 A Failure Catalogue for the LHC 2394
 
  • S. Wagner, R. Schmidt, B. Todd, J.A. Uythoven, M. Zerlauth
    CERN, Geneva, Switzerland
 
  The LHC, with a stored energy of more than 360 MJ per beam, requires a complex machine protection system to prevent equipment damage. The system was designed based on a large number of possible failures in the subsystems and operational phases of the LHC. This led to a mixed system with active and passive protection. The active part monitors many thousand parameters (such as beam losses, temperatures in superconducting magnets, power converter currents, etc.) and triggers a beam dump in case a failure is detected. The passive part includes protection elements like collimators and beam absorbers to ensure the prevention of damage in case of single turn beam losses (e.g. during beam transfer and injection). So far, the knowledge of the possible failures is distributed over the different teams involved in the design, construction and operation of the LHC. A newly started project aims at bringing together this knowledge in a common failure catalogue. The chosen approach in addition is expected to allow for the identification of failures that might not have been considered yet or that require further measures. This paper introduces the approach and presents the first experience.  
 
THPZ025 Stability of the LHC Transfer lines 3741
 
  • V. Kain, W. Bartmann, C. Bracco, L.N. Drosdal, B. Goddard, M. Meddahi, J.A. Uythoven, J. Wenninger
    CERN, Geneva, Switzerland
 
  The LHC is filled from the SPS through two 3 km transfer lines. The injected beam parameters need to be well under control for luminosity performance, machine protection and operational efficiency. Small fractions of beam loss on the transfer line collimation system create showers which can trigger the sensitive LHC beam loss monitor system nearby and cause a beam abort during filling. The stability of the transfer line trajectory through the collimators is particularly critical in this respect. This paper will report on the transfer line trajectory stability during the proton run in 2011, correlations with injection losses, correction frequency and the most likely sources for the observed oscillations.  
 
THPS055 Controlling Beamloss at Injection into the LHC 3553
 
  • B. Goddard, F. Alessio, W. Bartmann, P. Baudrenghien, V. Boccone, C. Bracco, M. Brugger, K. Cornelis, B. Dehning, A. Di Mauro, L.N. Drosdal, E.B. Holzer, W. Höfle, R. Jacobsson, V. Kain, M. Meddahi, V. Mertens, A. Nordt, J.A. Uythoven, D. Valuch, S. Weisz, E.N. del Busto
    CERN, Geneva, Switzerland
  • R. Appleby
    UMAN, Manchester, United Kingdom
 
  Losses at injection into the superconducting LHC can adversely affect the machine performance in several important ways. The high injected beam intensity and energy mean that precautions must be taken against damage and quenches, including collimators placed close to the beam in the injection regions. Clean injection is essential, to avoid spurious signals on the sensitive beam loss monitoring system which will trigger beam dumps. In addition, the use of the two injection insertions to house downstream high energy physics experiments brings constraints on permitted beam loss levels. In this paper the sources of injection beam loss are discussed together with the contributing factors and various issues experienced in the first full year of LHC operation. Simulations are compared with measurement, and the implemented and planned mitigation measures and diagnostic improvements are described. An outlook for future LHC operation is given.