| Paper |
Title |
Page |
| THPMN059 |
Feedback Studies
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2841 |
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- A. Latina, G. Rumolo, D. Schulte, R. Tomas
CERN, Geneva
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Funding: Supported by the European Community under the 6th Framework Programme "Structuring the European Research Area".
Dynamic imperfections in future linear colliders can lead to a significant luminosity loss. We discuss different orbit feedback strategies in the main linac that can mitigate the emittance dilution and compare their efficiency. We also address the impact of ground motion in the beam delivery system and the potential cures.
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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. 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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| THPAN068 |
Wakefield Models for Particle Tracking Codes
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3378 |
| |
- A. Latina, G. Rumolo, D. Schulte
CERN, Geneva
- R. J. Barlow, A. Bungau
UMAN, Manchester
- G. A. Blair
Royal Holloway, University of London, Surrey
- J. D.A. Smith
Lancaster University, Lancaster
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Wakefields have a considerable effect on beam dynamics and they must not be neglected for emittance growth studies, background estimates and other problems. The codes used for these problems are normally not capable of self-consistent wakefield calculations. They should thus be extended with either analytical models or export the wakefields numerically evaluated with other codes (such as Gdfidl) when analytical models are not feasible. We discuss both approaches and present their implementation in PLACET, MERLIN and BDSIM. The simulation results for the ILC and CLIC beam delivery systems are given as an example. Results produced with different codes are compared.
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| THPAN075 |
Modeling Incoherent Electron Cloud Effects
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3393 |
| |
- F. Zimmermann, E. Benedetto, G. Rumolo, D. Schulte, R. Tomas
CERN, Geneva
- W. Fischer
BNL, Upton, Long Island, New York
- G. Franchetti
GSI, Darmstadt
- K. Ohmi
KEK, Ibaraki
- M. T.F. Pivi, T. O. Raubenheimer
SLAC, Menlo Park, California
- K. G. Sonnad, J.-L. Vay
LBNL, Berkeley, California
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Incoherent effects driven by an electron cloud could seriously limit the beam lifetime in proton storage rings or blow up the vertical emittance in positron ones. Different approaches to modeling these effects each have their own merits and drawbacks. We compare the simulation results and computing time requirements from a number of dedicated codes under development over the last years, and describe the respective approximations for the beam-electron cloud interaction, the accelerator structure, and the optical lattice, made in each of these codes. Examples considered include the LHC, CERN SPS, RHIC, and the ILC damping ring. Tentative conclusions are drawn and a strategy for further codes development is outlined.
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| FRPMN065 |
Fast Vertical Single-Bunch Instability at Injection in the CERN SPS - An Update
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4162 |
| |
- G. Arduini, T. Bohl, H. Burkhardt, E. Metral, G. Rumolo
CERN, Geneva
- B. Salvant
EPFL, Lausanne
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Following the first observation of a fast vertical instability for a single high-brightness bunch at injection in the SPS in 2003, a series of detailed measurements and simulations has been performed in order to assess the resulting potential intensity limitations for the SPS, as well as possible cures. During the 2006 run, the characteristics of this instability were studied further, extending the intensity range of the measurements, and comparing the experimental data with simulations that take into account the latest measurements of the transverse machine impedance. In this paper, we summarize the outcome of these studies and our understanding of the mechanisms leading to this instability. The corresponding intensity limitations were also determined.
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| FRPMN074 |
Simulation Study of the Horizontal Head-Tail Instability Observed at Injection of the CERN Proton Synchrotron
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4210 |
| |
- E. Metral, G. Rumolo, R. R. Steerenberg
CERN, Geneva
- B. Salvant
EPFL, Lausanne
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For many years, a horizontal head-tail instability has been observed at the CERN Proton Synchrotron during the long 1.2 s injection flat-bottom. This slow instability has been damped using linear coupling only, i.e. with neither octupoles nor feedbacks. Using the nominal machine and beam parameters for LHC, the sixth head-tail mode number is usually observed. Several other modes were also observed in the past by tuning the chromaticity, and these observations were found to be in good agreement with Sacherer's formula. The purpose of this paper is to present the results of assessing the effect of chromaticity and linear coupling on this slow head-tail instability using the HEADTAIL simulation code, and to compare these simulations with both measurements performed over the last few years, and theoretical calculations.
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| FRPMN076 |
Nominal LHC Beam Instability Observations in the CERN Proton Synchrotron
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4222 |
| |
- R. R. Steerenberg, G. Arduini, E. Benedetto, A. Blas, W. Hofle, E. Metral, M. Morvillo, C. Rossi, G. Rumolo
CERN, Geneva
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The nominal LHC beam has been produced successfully in the CERN Proton Synchrotron since 2003. However, after having restarted the CERN PS in spring 2006, the LHC beam was set-up and observed to be unstable on the 26 GeV/c extraction flat top. An intensive measurement campaign was made to understand the instability and to trace its source. This paper presents the observations, possible explanations and the necessary measures to be taken in order to avoid this instability in the future.
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| FRPMN078 |
Improved Algorithms to Determine Non-Linear Optics Model of the SPS from Non-Linear Chromaticity
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4231 |
| |
- R. Tomas, G. Arduini, G. Rumolo, F. Zimmermann
CERN, Geneva
- R. Calaga
BNL, Upton, Long Island, New York
- A. Faus-Golfe
IFIC, Valencia
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Funding: This work is partially supported by the U. S. DOE
In recent years several measurements of the SPS non-linear chromaticity have been performed in order to determine the non-linear optics model of the SPS machine at injection energy for different cycles. In 2006 additional measurements have been performed at injection and during the ramp for the cycle used to accelerate the LHC beam. New and more robust matching algorithms have been developed in 2006 to fit the model to the measurements up to arbitrary chromatic order. In this paper we describe the algorithms used in the analysis of the data and we summarize and compare the results from all experiments.
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