| Paper |
Title |
Page |
| MPPE009 |
2003-2004 Nonlinear Optics Measurements and Modeling for the CERN SPS
|
1171 |
| |
- A. Faus-Golfe
IFIC, Valencia
- G. Arduini, F. Zimmermann
CERN, Geneva
- R. Tomas
CELLS, Bellaterra (Cerdanyola del Vallès)
|
|
| |
In 2003 and 2004 nonlinear chromaticity, amplitude detuning, chromatic phase advance, resonance driving terms and off-energy orbits were measured in the CERN SPS at 14 GeV/c and 26 GeV/c, respectively. From the nonlinear chromaticity, the SPS optics model has been updated, by adjusting the strength of nonlinear field errors in dipoles and quadrupoles. Furthermore, we have added to the model the effect of the displacement of all main bends and the voluntary misalignments of all the other elements of the machine. We compare the field errors with those founded in 2002, 2001 and 2000. The tune shifts with transverse amplitude, driving terms, etc., predicted by this nonlinear optics model are compared with direct measurements.
|
|
| TPAP007 |
LHC Collimation: Design and Results from Prototyping and Beam Tests
|
1078 |
| |
- R.W. Assmann, O. Aberle, G. Arduini, A. Bertarelli, H.-H. Braun, M. Brugger, H. Burkhardt, S. Calatroni, F. Caspers, E. Chiaveri, A. Dallocchio, B. Dehning, A. Ferrari, M. Gasior, A. Grudiev, E.B. Holzer, J.-B. Jeanneret, J.M. Jimenez, Y. Kadi, R. Losito, M. Magistris, A.M. Masi, M. Mayer, E. Métral, R. Perret, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, M. Santana-Leitner, D. Schulte, P. Sievers, E. Tsoulou, H. Vincke, V. Vlachoudis, J. Wenninger
CERN, Geneva
- I. Baishev, I.L. Kurochkin
IHEP Protvino, Protvino, Moscow Region
- G. Spiezia
Naples University Federico II, Science and Technology Pole, Napoli
|
|
| |
The problem of collimation and beam cleaning concerns one of the most challenging aspects of the LHC project. A collimation system must be designed, built, installed and commissioned with parameters that extend the present state-of-the-art by 2-3 orders of magnitude. Problems include robustness, cleaning efficiency, impedance and operational aspects. A strong design effort has been performed at CERN over the last two years. The system design has now been finalized for the two cleaning insertions. The adopted phased approach is described and the expected collimation performance is discussed. In parallel robust and precisely controllable collimators have been designed. Several LHC prototype collimators have been built and tested with the highest beam intensities that are presently available at CERN. The successful beam tests are presented, including beam-based setup procedures, a 2 MJ robustness test and measurements of the collimator-induced impedance. Finally, an outlook is presented on the challenges that are ahead in the coming years.
|
|
| TPAP008 |
Measurements of the LHC Collimator Impedance with Beam in the SPS
|
1132 |
| |
- 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
|
|
| |
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.
|
|
| TPAP015 |
Commissioning of the LHC Beam Transfer Line TI 8
|
1461 |
| |
- J.A. Uythoven, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, A. Spinks, J. Wenninger
CERN, Geneva
- Y.-C. Chao
Jefferson Lab, Newport News, Virginia
|
|
| |
The first of the two LHC transfer lines was commissioned in autumn 2004. Beam reached an absorber block located some 2.5 km downstream of the SPS extraction point at the first shot, without the need of any threading. The hardware preparation and commissioning phase will be summarised, followed by a description of the beam tests and their results regarding optics and other line parameters, including the experience gained with beam instrumentation, the control system and the machine protection equipment.
|
|
| TPAP016 |
Energy Calibration of the SPS with Proton and Lead Ion Beams
|
1470 |
| |
- J. Wenninger, G. Arduini, C. Arimatea, T. Bohl, P. Collier, K. Cornelis
CERN, Geneva
|
|
| |
The momentum of the 450 GeV/c proton beam of the CERN Super Proton Synchrotron was determined by a high precision measurement of the revolution frequencies of proton and lead ion beams. To minimize systematic errors the magnetic cycle of the SPS had to be rigorously identical for both beams, and corrections due to Earth tides had to be taken into account. This paper presents how the beam momentum was determined from the RF frequency for which the beams are centred in the machine sextupoles. The measured beam momentum is 449.16 ± 0.14 GeV/c for a nominal momentum of 450 GeV/c, and the accuracy is limited by systematic errors.
|
|
| TPAP018 |
Optics Studies of the LHC Beam Transfer Line TI8
|
1578 |
| |
- J. Wenninger, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, J.A. Uythoven
CERN, Geneva
- Y.-C. Chao
Jefferson Lab, Newport News, Virginia
|
|
| |
The optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated.
|
|
| ROPB004 |
Effect of Lattice and Electron Distribution in Electron-Cloud Instability Simulations for the CERN SPS and LHC
|
387 |
| |
- 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)
|
|
| |
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.
|
|
| ROPC004 |
Recent Intensity Increase in the CERN Accelerator Chain
|
413 |
| |
- E.N. Shaposhnikova, G. Arduini, T. Bohl, M. Chanel, R. Garoby, S. Hancock, K. Hanke, T.P.R. Linnecar, E. Métral, R.R. Steerenberg, B. Vandorpe
CERN, Geneva
|
|
| |
Future requests for protons from the physics community at CERN, especially after the start-up of the CNGS experiments in 2006, can only be satisfied by a substantial increase in the SPS beam intensity per pulse. In September 2004 a three weeks beam run was dedicated to high intensity; all accelerators in the chain were pushed to their limits to study intensity restrictions and find possible solutions. New record intensities were obtained in the accelerators of the PS & SPS Complex with this fixed-target type beam which is different from the nominal LHC beam. The challenges in producing this high-intensity beam are described together with the measures needed to make it fully operational.
|
|
| FPAP014 |
Electron Cloud Measurements in the SPS in 2004
|
1371 |
| |
- D. Schulte, G. Arduini, V. Baglin, J.M. Jimenez, F. Zimmermann
CERN, Geneva
|
|
| |
Novel measurements of the electron cloud have been performed in the SPS in 2004. In this machine the beam consists of a number of short bunch trains. By varying the distance between these trains it is possible to witness the survival of the electrons after the bunch passage. In this paper, results from simulations and experiments are compared.
|
|
| FPAT022 |
Performance of the CERN SPS Fast Extraction for the CNGS Facility
|
1757 |
| |
- E.H.R. Gaxiola, G. Arduini, W. Höfle, F. Roncarolo, E. Vogel, E. Vossenberg
CERN, Geneva
|
|
| |
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.
|
|