Author: Fuster, N.
Paper Title Page
MOPS017 Simulation Studies of Macro-particles Falling into the LHC Proton Beam 634
 
  • F. Zimmermann, T. Baer, M. Giovannozzi, E.B. Holzer, E. Nebot Del Busto, A. Nordt, M. Sapinski
    CERN, Geneva, Switzerland
  • N. Fuster
    Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
  • Z. Yang
    EPFL, Lausanne, Switzerland
 
  We report updated simulations on the interaction of macro-particles falling from the top of the vacuum chamber into the circulating LHC proton beam. The path and charge state of micron size micro-particles are computed together with the resulting beam losses, which – if high enough - can lead to the local quench of SC magnets. The simulated time evolution of the beam loss is compared with observations in order to constrain some macro-particle parameters. We also discuss the possibility of a "multiple crossing" by the same macro-particle, the effect of a strong dipole field, and the dependence of peak loss rate and loss duration on beam current and on beam size.  
 
TUPC136 Analysis of Fast Losses in the LHC with the BLM System 1344
 
  • E. Nebot Del Busto, T. Baer, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, A. Marsili, A. Nordt, M. Sapinski, R. Schmidt, B. Velghe, J. Wenninger, C. Zamantzas, F. Zimmermann
    CERN, Geneva, Switzerland
  • N. Fuster
    Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
  • Z. Yang
    EPFL, Lausanne, Switzerland
 
  About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 us to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. During the 2010 run, a limiting factor in the machine availability were sudden losses appearing around the ring on the ms time scale and detected exclusively by the BLM system. It is believed that such losses originate from dust particles falling into the beam, or being attracted by its strong electromagnetic field. This document describes some of the properties of these "Unidentified Falling Objects" (UFOs) putting special emphasis on their dependence on beam parameters (energy, intensity, etc). The subsequent modification of the BLM beam abort thresholds for the 2011 run that were made to avoid unnecessary beam dumps caused by these UFO losses are also discussed.