| Paper |
Title |
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| MOPAN074 |
Influence of Varying Tune Width on the Robustness of the LHC Tune PLL and its Application for Continuous Chromaticity Measurement
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326 |
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- R. J. Steinhagen
- A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski
CERN, Geneva
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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.
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| TUOCC02 |
Progress in Tune, Coupling, and Chromaticity Measurement and Feedback during RHIC Run 7
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886 |
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- P. Cameron
- J. Cupolo, W. C. Dawson, C. Degen, A. Della Penna, L. T. Hoff, Y. Luo, A. Marusic, R. Schroeder, C. Schultheiss, S. Tepikian
BNL, Upton, Long Island, New York
- M. Gasior
CERN, Geneva
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Funding: US DOE
Tune feedback was first implemented in RHIC in 2002 as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End. Continuous measurement of all projections of the betatron Eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort. The results of investigations of power line harmonics in RHIC are presented elsewhere in these proceedings.
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Slides
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| WEOAC03 |
Transverse Impedance of LHC Collimators
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2003 |
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- E. Metral
- G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. B. 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
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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.
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Slides
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| FRPMN073 |
The FPGA-based Continuous FFT Tune Measurement System for the LHC and its Test at the CERN SPS
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4204 |
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- A. Boccardi
- M. Gasior, O. R. Jones, K. K. Kasinski, R. J. Steinhagen
CERN, Geneva
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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.
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