Author: Boccardi, A.
Paper Title Page
MOEPPB010 Measurement of Satellite Bunches at the LHC 97
  • A. Jeff, M. Andersen, A. Boccardi, S. Bozyigit, E. Bravin, T. Lefèvre, A. Rabiller, F. Roncarolo
    CERN, Geneva, Switzerland
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  Funding: Adam Jeff is a DITANET fellow, supported by the EU's Marie Curie actions contract PITN-GA-2008-215080.
The RF gymnastics involved in the delivery of proton and lead ion bunches to the LHC can result in satellite bunches of varying intensity occupying the nominally empty RF buckets. Quantification of these satellites is crucial for bunch-by-bunch luminosity normalization as well as for machine protection. We present an overview of the longitudinal density monitor (LDM) which is the principal instrument for the measurement of satellite bunches in the LHC. The LDM uses single photon counting of synchrotron light. The very high energies reached in the LHC, combined with a dedicated undulator for diagnostics, allow synchrotron light measurements to be made with both protons and heavy ions. The arrival times of photons are collected over a few million turns, with the resulting histogram corrected for the effects of the detector’s deadtime and afterpulsing in order to reconstruct the longitudinal profile of the entire LHC ring. The LDM has achieved a dynamic range in excess of 105 and a time resolution of 90 ps. Example results are presented and the measurements are benchmarked against satellite distributions based on collision data from the LHC experiments.
MOPPD058 LHC Abort Gap Cleaning Studies during Luminosity Operation 496
  • E. Gianfelice-Wendt
    Fermilab, Batavia, USA
  • W. Bartmann, A. Boccardi, C. Bracco, E. Bravin, B. Goddard, W. Höfle, D. Jacquet, A. Jeff, V. Kain, M. Meddahi, F. Roncarolo, J.A. Uythoven, D. Valuch
    CERN, Geneva, Switzerland
  The presence of significant intensities of un-bunched beam is a potentially serious issue in the LHC. Procedures using damper kickers for cleaning both Abort Gap (AG) and buckets targeted for injection, are currently in operation at flat bottom. Recent observations of relatively high population of the AG during physics runs brought up the need for AG cleaning during luminosity operation as well. In this paper the results of experimental studies performed in October 2011 are presented.