Paper |
Title |
Page |
TUPWA039 |
Identification of the SPS Impedance at 1.4 GHz |
1793 |
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- T. Argyropoulos, T. Bohl, H. Damerau, J.F. Esteban Müller, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland
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In the SPS spectrum measurements of very long single bunches were used in the past to identify sources of longitudinal microwave instability. Shielding of the identified objects significantly improved the beam stability. However, longitudinal instabilities are still one of the limitations for high intensity LHC beams in the SPS. Recently the same measurement technique was used again, revealing a strong high frequency resonance. During the slow de-bunching with the RF switched off, the presence of different resonant impedances leads to a line density modulation at the resonant frequencies. Longitudinal profiles of bunches of various intensities were acquired. For sufficiently high intensities their spectra show a fast growing and strong modulation at 1.4 GHz. Measurements using two transverse optics with different transition energy are compared. Reproducing the measurements with numerical simulations, including the known SPS longitudinal impedances, allowed the parameter range of this unknown source to be determined. Possible candidates as impedance sources in the SPS ring are investigated.
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TUPWA044 |
Longitudinal Coupled-Bunch Oscillation Studies in the CERN PS |
1808 |
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- H. Damerau, S. Hancock, M.M. Paoluzzi
CERN, Geneva, Switzerland
- M. Migliorati, L. Ventura
Rome University La Sapienza, Roma, Italy
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Longitudinal coupled-bunch oscillations are an important limitation for the high-brightness beams accelerated in the CERN PS. Up to the present intensities they are suppressed by a dedicated feedback system limited to the two dominant oscillation modes. In view of the proposed installation of a wide-band feedback kicker cavity within the framework of the LHC Injectors Upgrade project (LIU), measurements have been performed with the existing damping system with the aim of dimensioning the new one. Following the excitation of well-defined oscillation modes, damping times and corresponding longitudinal kick strength are analysed. The paper summarizes the results of the observations and gives an outlook on the expected performance with the new coupled-bunch feedback.
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WEPEA013 |
Electron Cloud Studies for the Upgrade of the CERN PS |
2522 |
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- G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy
- H. Damerau, S.S. Gilardoni, G. Iadarola, S. Rioja Fuentelsaz, G. Rumolo, G. Sterbini, C. Yin Vallgren
CERN, Geneva, Switzerland
- M.T.F. Pivi
SLAC, Menlo Park, California, USA
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The observation of a significant dynamic pressure rise as well as measurements with dedicated detectors indicate that an electron cloud develops in the CERN PS during the last stages of the RF manipulations for the production of LHC type beams, especially with 25ns bunch spacing. Although presently these beams are not degraded by the interaction with the electron cloud, which develops only during few milliseconds before extraction, the question if this effect could degrade the future high intensity and high brightness beams foreseen by the LHC Injectors Upgrade (LIU) project is still open. Therefore several studies are being carried out employing both simulations and measurements with the electron cloud detectors in the machine. The aim is to develop a reliable electron cloud model of the PS vacuum chambers in order to identify possible future limitations and find suitable countermeasures.
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WEPEA042 |
The PS Upgrade Programme: Recent Advances |
2594 |
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- S.S. Gilardoni, S. Bart Pedersen, C. Bertone, N. Biancacci, A. Blas, D. Bodart, J. Borburgh, P. Chiggiato, H. Damerau, S. Damjanovic, J.D. Devine, T. Dobers, M. Gourber-Pace, S. Hancock, A. Huschauer, G. Iadarola, L.A. Lopez Hernandez, A. Masi, S. Mataguez, E. Métral, M.M. Paoluzzi, S. Persichelli, S. Pittet, S. Roesler, C. Rossi, G. Rumolo, B. Salvant, R. Steerenberg, G. Sterbini, L. Ventura, J. Vollaire, R. Wasef, C. Yin Vallgren
CERN, Geneva, Switzerland
- M. Migliorati
University of Rome "La Sapienza", Rome, Italy
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The LHC Injectors Upgrade project (LIU) has been initiated to improve the performances of the existing injector complex at CERN to match the future requirements of the HL-LHC. In this framework, the Proton Synchrotron (PS) will undergo fundamental changes for many of its main systems: the injection energy will be increased to reduce space-charge effects, the transverse damper will be improved to cope with transverse instabilities the RF systems will be upgraded to accelerate higher beam intensity and brightness. These hardware improvements are triggered by a series of studies meant to identify the most critical performance bottlenecks, like space charge, impedances, longitudinal and transverse instabilities, as well as electron-cloud. Additionally, alternative production schemes for the LHC-type beams have been proposed and implemented to circumvent some of the present limitations. A summary of the most recent advances of the studies, as well as the proposed hardware improvements is given.
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WEPEA043 |
Working Point and Resonance Studies at the CERN PS |
2597 |
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- A. Huschauer, M. Benedikt, H. Damerau, P. Freyermuth, S.S. Gilardoni, R. Steerenberg, B. Vandorpe
CERN, Geneva, Switzerland
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The increase of luminosity demanded by the High Luminosity LHC (HL-LHC) requires an increase of beam intensity, which might result in instabilities appearing at injection energy in the CERN PS. Transverse head-tail instabilities have already been observed on operational LHC beams and a stabilizing mechanism as an alternative to linear coupling is currently being studied. It consists of reducing the mode number of the transverse oscillation by changing linear chromaticity and in succession completely suppressing the instability by a transverse damper system with appropriate bandwidth. Therefore, a chromaticity correction scheme at low energy exploiting the intrinsic possibilities offered by special circuits mounted on top of the main magnet poles, the Pole Face Windings (PFW), has been examined. The presence of destructive betatron resonances, which restrict the choice of the injection working point and the maximum acceptable tune spread, forms an additional limitation for high-brightness and high-intensity beams in the CERN PS. To improve the current working point control scheme, the influence of the P F W on the machine resonances is presented in this paper.
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WEPEA044 |
RF Manipulations for Higher Brightness LHC-type Beams |
2600 |
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- H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock
CERN, Geneva, Switzerland
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In order to increase the transverse brightness of beams for the LHC, ever more complicated RF manipulations have been proposed in the PS machine in order to reduce the intensity demands per PS batch on the upstream PS Booster. Several schemes based on cascades of batch compression, bunch merging, as well as the more routine bunch splitting have been successfully commissioned and higher brightness beams have been delivered to the downstream accelerators for measurement. Despite all this complexity, longitudinal and transverse beam quality are well preserved. In addition, to fully profit from the brightness of all four PS Booster rings, the injection of twice 4 bunches into harmonic 9 buckets in the PS has been made operational as an alternative to the usual double-batch transfer of 4+2 bunches into harmonic 7. This paper summarizes the new beam production schemes, their implementation in the PS low-level RF system and the experimental results.
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WEPEA053 |
Progress with the Upgrade of the SPS for the HL-LHC Era |
2624 |
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- B. Goddard, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, F. Caspers, K. Cornelis, H. Damerau, L.N. Drøsdal, L. Ducimetière, J.F. Esteban Müller, R. Garoby, M. Gourber-Pace, W. Höfle, G. Iadarola, L.K. Jensen, V. Kain, R. Losito, M. Meddahi, A. Mereghetti, V. Mertens, Ö. Mete, E. Montesinos, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, M. Taborelli, H. Timko, F.M. Velotti
CERN, Geneva, Switzerland
- E. Gianfelice-Wendt
Fermilab, Batavia, USA
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The demanding beam performance requirements of the HL-LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed.
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WEPEA060 |
Plans for the Upgrade of CERN's Heavy Ion Complex |
2645 |
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- D. Manglunki, M. E. Angoletta, H. Bartosik, A. Blas, D. Bodart, M.A. Bodendorfer, T. Bohl, J. Borburgh, E. Carlier, J.-M. Cravero, H. Damerau, L. Ducimetière, A. Findlay, R. Garoby, S.S. Gilardoni, B. Goddard, S. Hancock, E.B. Holzer, J.M. Jowett, T. Kramer, D. Kuchler, A.M. Lombardi, Y. Papaphilippou, S. Pasinelli, R. Scrivens, G. Tranquille
CERN, Geneva, Switzerland
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To reach a luminosity higher than 6×1027 Hz/cm2 for Pb-Pb collisions, as expected by the ALICE experiment after its upgrade during the 2nd Long LHC Shutdown (LS2), several upgrades will have to be performed in the CERN accelerator complex, from the source to the LHC itself. This paper first details the present limitations and then describes the strategy for the different machines in the ion injector chain. Both filling schemes and possible hardware upgrades are discussed.
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WEPEA061 |
The First LHC p-Pb run: Performance of the Heavy Ion Production Complex |
2648 |
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- D. Manglunki, M. E. Angoletta, H. Bartosik, G. Bellodi, A. Blas, M.A. Bodendorfer, T. Bohl, C. Carli, E. Carlier, S. Cettour Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, J.M. Jowett, D. Kuchler, M. O'Neil, Y. Papaphilippou, S. Pasinelli, R. Scrivens, G. Tranquille, B. Vandorpe, U. Wehrle, J. Wenninger
CERN, Geneva, Switzerland
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TThe first LHC proton-ion run took place in January-February 2013; it was the first extension to the collider programme, as this mode was not included in the design report. This paper presents the performance of the heavy ion and proton production complex, and details the issues encountered, in particular the creation of the same bunch pattern in both beams.
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WEPEA070 |
Space Charge Effects and Limitations in the Cern Proton Synchrotron |
2669 |
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- R. Wasef, G. Arduini, H. Damerau, S.S. Gilardoni, S. Hancock, C. Hernalsteens, A. Huschauer, F. Schmidt
CERN, Geneva, Switzerland
- G. Franchetti
GSI, Darmstadt, Germany
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Space charge produces a large incoherent tune-spread which, in presence of betatronic resonances, could lead to beam losses and emittance growth. In the CERN Proton Synchrotron, at the current injection kinetic energy (1.4 GeV) and even at the future kinetic energy (2 GeV), space charge is one of the main limitations for high brightness beams and especially for the future High-Luminosity LHC beams. Several detailed studies and measurements have been carried out to improve the understanding of space charge limitations to determine the maximum acceptable tune spread and identify the most important resonances causing losses and emittance growth.
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THPWO077 |
Status and Plans for the Upgrade of the LHC Injectors |
3936 |
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- R. Garoby, H. Damerau, S.S. Gilardoni, B. Goddard, K. Hanke, A.M. Lombardi, D. Manglunki, M. Meddahi, B. Mikulec, L. Ponce, E.N. Shaposhnikova, R. Steerenberg, M. Vretenar
CERN, Geneva, Switzerland
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The plans for preparing the LHC injectors to fulfill the needs of the LHC during the next decade have significantly progressed in 2012. Linac4 construction has passed major steps of pre-series fabrication. Hardware developments and beam studies have allowed refining the baseline actions to implement and the beam characteristics achievable at injection into the collider for protons as well as for Lead ions. These achievements are described in this paper, together with the updated project planning matched to the new schedule of the LHC.
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