| Paper |
Title |
Page |
| TUPP091 |
WISE: a Simulation of the LHC Optics Including Magnet Geometrical Data
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1744 |
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- P. Hagen, M. Giovannozzi, J.-P. Koutchouk, T. Risselada, F. Schmidt, E. Todesco, E. Y. Wildner
CERN, Geneva
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The beam dynamics in LHC strongly depends on the field quality and geometry of the magnets. A model of the LHC optics has been built, based on the information available at the end of the production as well as on statistical evaluations for the missing information The pre-processor WISE generates instances of the LHC field errors for the MAD X program, with the possibility of selecting various sources. This paper describes the progress since WISE was presented in EPAC06. The slot allocation in LHC is completed since all magnets are installed and interconnected. Geometric measurements have been added for all magnets. Furthermore, some statistical data is available relative to the precision of magnet installation (alignment) and tunnel movements. In this paper the code and the data are used to update the beta-beating estimate at injection and collision energy. The relevance of misalignments of the different magnets and their impact on beta-beating is compared to the sources that have been previously considered, i.e. the spread in the gradient of the cell quadrupoles and the uncertainty associated to the knowledge of the transfer functions of the stand-alone quadrupoles.
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| WEPP003 |
Optics Flexibility in the LHC at Top Energy
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2524 |
| |
- M. Aiba, H. Burkhardt, S. D. Fartoukh, M. Giovannozzi, S. M. White
CERN, Geneva
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We report on studies of optics flexibility which allow for tune changes of the order of half a unit at top energy in the LHC. We describe how this could be done using one or several of the insertions IR2, IR4, IR8 or the main quadrupoles and discuss and compare the implications. This flexibility could be used to compensate for the loss in tune for high beta optics and may make it feasible to use the standard injection and ramp for these configurations. Potential further applications are also highlighted.
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| WEPP012 |
Analysis of Optical Layouts for the Phase 1 Upgrade of the CERN Large Hadron Collider Insertion Regions
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2551 |
| |
- M. Giovannozzi, F. Borgnolutti, O. S. Brüning, U. Dorda, S. D. Fartoukh, W. Herr, M. Meddahi, E. Todesco, R. Tomas, F. Zimmermann
CERN, Geneva
- R. de Maria
EPFL, Lausanne
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In the framework of the studies for the upgrade of the insertions of the CERN Large Hadron Collider, four optical layouts were proposed with the aim of reducing the beta-function at the collision point down to 25 cm. The different candidate layouts are presented. Results from the studies performed on mechanical and dynamic aperture are summarized, together with the evaluation of beam-beam effects. Particular emphasis is given to the comparison of the optics performance, which led to retain two promising layouts for further investigation and development.
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| WEPP024 |
Non-linear Correction Schemes for the Phase 1 LHC Insertion Region Upgrade and Dynamic Aperture Studies
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2569 |
| |
- R. Tomas, M. Giovannozzi, R. de Maria
CERN, Geneva
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The Phase 1 LHC Interaction Region (IR) upgrade aims at increasing the machine luminosity essentially by reducing the beam size at the Interaction Point (IP). This requires a total redesign of the full IR. A large set of options have been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the multipolar errors of the IR magnets in the design phase. The goal is to use the same correction approach for the different designs. The correction algorithm is based on the computation of the IR transfer map. Its performance is tested using the dynamic aperture as figure of merit.
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| THPC049 |
Progress in the Beam Preparation for the Multi-turn Extraction at the CERN Proton Synchrotron
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3089 |
| |
- S. S. Gilardoni, F. Franchi, M. Giovannozzi
CERN, Geneva
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A new type of extraction based on beam trapping inside stable islands in the horizontal phase space will become operational during 2008 at the CERN Proton Synchrotron. A series of beam experiments was carried out to prove loss-less capture with high intensity and multi-bunched beams, up to 1500·1010 protons per pulse, in preparation of the extraction commissioning. These fundamental steps for the new Multi-turn Extraction are presented and discussed in details.
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| THPC050 |
Experimental Evidence of Beam Trapping with One-third and One-fifth Resonance Crossing
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3092 |
| |
- S. S. Gilardoni, F. Franchi, M. Giovannozzi
CERN, Geneva
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Beam trapping in stable islands of the horizontal phase space generated by non-linear magnetic fields is realized by means of a given tune variation so to cross a resonance of order n. Whenever the resonance is stable, n+1 beamlets are created whereas if the resonance is unstable, the beam is split in n parts. Experiments at the CERN Proton Synchrotron showed protons trapped in stable islands while crossing the one-third and one-fifth resonance with the creation of 3 and 6 stable beamlets, respectively. The results are presented and discussed in details.
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| THPC051 |
Adiabaticity and Reversibility Studies for Beam Splitting Using Stable Resonances
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3095 |
| |
- S. S. Gilardoni, F. Franchi, M. Giovannozzi
CERN, Geneva
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At the CERN Proton Synchrotron, a series of beam experiments proved beam splitting by crossing the one-fourth resonance. Depending on the speed at which the horizontal resonance is crossed, the splitting process is more or less adiabatic, and a different fraction of the initial beam is trapped in the islands. Experiments prove that when the trapping process is reversed and the islands merged together, the final distribution features thick tails. The beam population in such tails is correlated to the speed of the resonance crossing and to the fraction of the beam trapped in the stable islands. Experiments, simulations, and possible theoretical explanations are discussed.
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| THPC056 |
Stability Change of Fourth-order Resonance with Application to Multi-turn Extraction Schemes
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3110 |
| |
- M. Giovannozzi, D. Quatraro
CERN, Geneva
- G. Turchetti
Bologna University, Bologna
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Recently, a novel multi-turn extraction scheme was proposed, based on particle trapping inside stable resonances. Numerical simulations and experimental tests confirmed the feasibility of such a scheme for low order resonances. While the 3rd order resonance is generically unstable and those higher than 4th order are generically stable, the 4th order resonance can be either stable or unstable depending on the details of the system under consideration. By means of the normal form approach a general formula to control the stability of the 4th order resonance is derived. Numerical simulations confirm the analytical results and show that by crossing the unstable 4th order resonance the region around the centre of phase space is depleted and particles are trapped only in the four stable islands. This indicates that a four-turn extraction could be envisaged based on this technique.
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