| Paper |
Title |
Page |
| TUPP050 |
Electron Cloud Mitigation by Fast Bunch Compression in the CERN PS
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1658 |
| |
- H. Damerau, S. Hancock, T. Kroyer, E. Mahner, M. Schokker
CERN, Geneva
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A fast transverse instability has been observed with nominal LHC beams in the CERN Proton Synchrotron (PS) in 2006. The instability develops within less than 1 ms, starting when the bunch length decreases below a threshold of 11.5 ns during the RF procedure to shorten the bunches immediately prior to extraction. An alternative longitudinal beam manipulation, double bunch rotation, has been proposed to compress the bunches from 14 ns to the 4 ns required at extraction within 0.9 ms, saving some 4.5 ms with respect to the present compression scheme. The resultant bunch length is found to be equivalent for both schemes. In addition, electron cloud and vacuum measurements confirm that the development of an electron cloud and the onset of an associated fast pressure rise are delayed with the new compression scheme. Beam dynamics simulations and measurements of the double bunch rotation are presented as well as evidence for its beneficial effect from the electron cloud standpoint.
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| MOPC131 |
Ions for LHC: Towards Completion of the Injector Chain
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376 |
| |
- D. Manglunki, M. Albert, M.-E. Angoletta, G. Arduini, P. Baudrenghien, G. Bellodi, P. Belochitskii, E. Benedetto, T. Bohl, C. Carli, E. Carlier, M. Chanel, H. Damerau, S. S. Gilardoni, S. Hancock, D. Jacquet, J. M. Jowett, V. Kain, D. Kuchler, M. Martini, S. Maury, E. Métral, L. Normann, G. Papotti, S. Pasinelli, M. Schokker, R. Scrivens, G. Tranquille, J. L. Vallet, B. Vandorpe, U. Wehrle, J. Wenninger
CERN, Geneva
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The CERN LHC experimental programme includes heavy ion physics with collisions between two counter-rotating Pb82+ ion beams at a momentum of 2.76 TeV/c/nucleon per beam and luminosities as high as 1·1027 cm-2 s-1. To achieve the beam parameters required for this operation the ion accelerator chain has undergone substantial modifications. Commissioning with beam of the various elements of this chain started in 2005 and in 2007 it was the turn of the final stage, the Super-Proton-Synchrotron (SPS) following extensive changes to the low-level RF hardware. The major limitations of this mode of operation of the SPS (space charge, intra-beam scattering) are presented, together with the performance reached so far. The status of the pre-injector performance will also be reviewed together with a description of the steps required to reach nominal performance.
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| TUPP066 |
CERN SPS Impedance in 2007
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1691 |
| |
- E. Métral, G. Arduini, T. Bohl, H. Burkhardt, F. Caspers, H. Damerau, T. Kroyer, H. Medina, G. Rumolo, M. Schokker, E. N. Shaposhnikova, J. Tuckmantel
CERN, Geneva
- R. Calaga
BNL, Upton, Long Island, New York
- B. Salvant
EPFL, Lausanne
- B. Spataro
INFN/LNF, Frascati (Roma)
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Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet.
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| THPC121 |
LHC Transverse Feedback System and its Hardware Commissioning
|
3266 |
| |
- W. Höfle, P. Baudrenghien, F. Killing, Y. A. Kojevnikov, G. Kotzian, R. Louwerse, E. Montesinos, V. Rossi, M. Schokker, E. Thepenier, D. Valuch
CERN, Geneva
- E. V. Gorbachev, N. I. Lebedev, A. A. Makarov, S. Rubtsun, V. Zhabitsky
JINR, Dubna, Moscow Region
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A powerful transverse feedback system ('damper') has been installed in LHC. It will stabilise coupled bunch instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The transverse damper can also be used as an exciter for purposes of abort gap cleaning or tune measurement. The power and low-level systems layout are described along with results from the hardware commissioning. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control. Requirements and first measurements of the performance of the low-level system are summarized. The chosen approach for the low-level system using advanced FPGA technology is very flexible allowing implementation of future upgrades of the signal processing without changing the hardware.
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