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Jones, O. R.

Paper Title Page
MOPAN074 Influence of Varying Tune Width on the Robustness of the LHC Tune PLL and its Application for Continuous Chromaticity Measurement 326
  • R. J. Steinhagen, A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski
    CERN, Geneva
  Tune and chromaticity measurement is an integral part for safe and reliable LHC operation. Tight tolerances on the maximum transverse beam excursions allow oscillation amplitudes of less than 30 um. This leaves only a small margin for transverse beam and momentum excitations required for measuring tune and chromaticity. This contribution discusses a robust tune phase-locked-loop (PLL) operation in the presence of non-linearities and varying chromaticity. The loop design was tested at the SPS, using the LHC PLL prototype system. The system was also used to continuously measure tune width and chromaticity, using resonant transverse excitations of the tune side-slopes.  
WEOAC03 Transverse Impedance of LHC Collimators 2003
  • E. Metral, G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. Bracco, F. Caspers, M. Gasior, O. R. Jones, K. K. Kasinski, T. Kroyer, S. Redaelli, G. Robert-Demolaize, G. Rumolo, R. J. Steinhagen, Th. Weiler, F. Zimmermann
    CERN, Geneva
  • F. Roncarolo
    UMAN, Manchester
  • B. Salvant
    EPFL, Lausanne
  The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.  
slides icon Slides  
THXC01 LHC Beam Instrumentation 2630
  • O. R. Jones
    CERN, Geneva
  The LHC will have very tight tolerances on all beam parameters. Their precise measurement is therefore very important for controlling and understanding the machine. With over two orders of magnitude higher stored beam energy than previous colliders, machine protection is also an issue, with any beam losses having to be closely monitored. This presentation will aim to give an overview of the beam instrumentation foreseen for the LHC together with the requirements for initial and nominal operation. A summary of the main systems will be followed by a discussion of areas where there have been recent advances, such as in the measurement of tune, chromaticity and coupling.  
slides icon Slides  
FRPMN068 The 4.8 GHz LHC Schottky Pick-up System 4174
  • F. Caspers, J. M. Jimenez, O. R. Jones, T. Kroyer, VC. Vuitton
    CERN, Geneva
  • T. W. Hamerla, A. Jansson, J. R. Misek, R. J. Pasquinelli, P. C. Seifrid, D. Sun, D. G. Tinsley
    Fermilab, Batavia, Illinois
  Funding: LARP

The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down-mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed.

FRPMN073 The FPGA-based Continuous FFT Tune Measurement System for the LHC and its Test at the CERN SPS 4204
  • A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski, R. J. Steinhagen
    CERN, Geneva
  A base band tune (BBQ) measurement system has been developed at CERN. This system is based on a high-sensitivity direct-diode detection technique followed by a high resolution FFT algorithm implemented in an FPGA. The system allows acquisition of continuous real-time spectra with 32-bit resolution, while a digital frequency synthesiser (DFS) can provide an acquisition synchronised chirp excitation. All the implemented algorithms support dynamic reconfiguration of processing and excitation parameters. Results from both laboratory measurements and tests performed with beam at the CERN SPS are presented.