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Title |
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| MOPC009 |
Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004
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686 |
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- F. Zimmermann, J.-P. Koutchouk, F. Roncarolo, J. Wenninger
CERN, Geneva
- Y. Papaphilippou
ESRF, Grenoble
- T. Sen, V.D. Shiltsev
Fermilab, Batavia, Illinois
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Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS compensators were also used to 'simulate' the effect of different planes of crossing at two LHC interaction points. We present the experimental results and compare them with computer simulations.
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| TOPC005 |
Transverse Emittance Blow-Up Due to the Operation of Wire Scanners, Analytical Predictions and Measurements
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437 |
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- F. Roncarolo, B. Dehning
CERN, Geneva
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Wire Scanner monitors are used in the CERN accelerators to measure the transverse beam size. In the SPS and the LHC they will serve as calibration devices for other emittance monitors. The PSB, PS and SPS are equipped with scanners which move through the beam a 30 um wire, with a speed that can vary between 0.4 to 20 m/s. During each scan, the beam suffers an emittance blow up, due to multiple Coulomb scattering of the beam protons on the lattice nuclei of the wire material. The effect depends on the particles' energy, the betatron function at the monitor location and on the wire characteristics (material, diameter and speed). In this paper we will present a comparison of the analytically predicted emittance increase caused by the instruments and a number of experimental measurements. For the small LHC beams the relative emittance blow-up can exceed a few 10e-2.
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| TPAP008 |
Measurements of the LHC Collimator Impedance with Beam in the SPS
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1132 |
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- H. Burkhardt, G. Arduini, R.W. Assmann, F. Caspers, M. Gasior, A. Grudiev, O.R. Jones, T. Kroyer, E. Métral, S. Redaelli, G. Robert-Demolaize, F. Roncarolo, D. Schulte, R.J. Steinhagen, J. Wenninger, F. Zimmermann
CERN, Geneva
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The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results.
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| ROPB004 |
Effect of Lattice and Electron Distribution in Electron-Cloud Instability Simulations for the CERN SPS and LHC
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387 |
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- E. Benedetto, E. Benedetto
Politecnico di Torino, Torino
- G. Arduini, F. Roncarolo, F. Zimmermann
CERN, Geneva
- B. Feng, A.F. Ghalam, T.C. Katsouleas
USC, Los Angeles, California
- G. Franchetti
GSI, Darmstadt
- K. Ohmi
KEK, Ibaraki
- G. Rumolo
CELLS, Bellaterra (Cerdanyola del Vallès)
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Several simulation codes have been adapted so as to model the single-bunch electron-cloud instability including a realistic variation of the optical functions with longitudinal position. In addition, the electron cloud is typically not uniformly distributed around the ring, as frequently assumed, but it is mainly concentrated in certain regions with specific features, e.g., regions which give rise to strong multipacting or suffer from large synchrotron radiation flux. Particularly, electrons in a dipole magnet are forced to follow the vertical field lines and, depending on the bunch intensity, they may populate two vertical stripes, symmetrically located on either side of the beam. In this paper, we present simulation results for the CERN SPS and LHC, which can be compared with measurements or analytical predictions.
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| FPAT022 |
Performance of the CERN SPS Fast Extraction for the CNGS Facility
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1757 |
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- E.H.R. Gaxiola, G. Arduini, W. Höfle, F. Roncarolo, E. Vogel, E. Vossenberg
CERN, Geneva
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The SPS LSS4 fast extraction system will serve both the anti-clockwise ring of the LHC and the long baseline neutrino (CNGS) facility. For the latter two extractions spaced by 50 ms, each affecting half of the ring, are foreseen. During the shutdown 2003-2004 the performance of the fast extraction kickers was improved in order to match more closely the specifications for the kicker pulse shape required for the CNGS and LHC extractions. The rise and fall times were significantly reduced, as well as the post-pulse kick ripple. However, the latter remains outside specifications and oscillations are induced in the leading bunches of the batch remaining in the machine at the moment of the first extraction. While further improving the characteristics of the kicker pulse shape, the possibility of damping the beam oscillations using the transverse feedback system has been explored. We report on the recent pulse form improvements and results of beam tests.
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