Paper |
Title |
Page |
MOPS016 |
First Observations of Intensity-dependent Effects for Transversally Split Beams |
631 |
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- S.S. Gilardoni, M. Giovannozzi
CERN, Geneva, Switzerland
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During the commissioning of the CERN PS Multi-Turn Extraction (MTE) tests with different beam intensities were performed. The beam current before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total intensity was found, which is a first observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in this paper.
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MOPS017 |
Simulation Studies of Macro-particles Falling into the LHC Proton Beam |
634 |
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- F. Zimmermann, T. Baer, M. Giovannozzi, E.B. Holzer, E. Nebot Del Busto, A. Nordt, M. Sapinski
CERN, Geneva, Switzerland
- N. Fuster
Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
- Z. Yang
EPFL, Lausanne, Switzerland
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We report updated simulations on the interaction of macro-particles falling from the top of the vacuum chamber into the circulating LHC proton beam. The path and charge state of micron size micro-particles are computed together with the resulting beam losses, which – if high enough - can lead to the local quench of SC magnets. The simulated time evolution of the beam loss is compared with observations in order to constrain some macro-particle parameters. We also discuss the possibility of a "multiple crossing" by the same macro-particle, the effect of a strong dipole field, and the dependence of peak loss rate and loss duration on beam current and on beam size.
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TUPZ006 |
Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan |
1810 |
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- R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann
CERN, Geneva, Switzerland
- M. Alabau
IFIC, Valencia, Spain
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A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in σs of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.
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WEPC032 |
First Measurements of Higher Order Optics Parameters in the LHC |
2073 |
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- G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands
- M. Aiba
PSI, Villigen, Switzerland
- R. Bartolini
Diamond, Oxfordshire, United Kingdom
- R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
- M. Giovannozzi, F. Schmidt, R. Tomás
CERN, Geneva, Switzerland
- E.H. Maclean
JAI, Oxford, United Kingdom
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Higher order effects can play an important role in the performance of the LHC. Lack of knowledge of these parameters can increase the tune footprint and compromise the beam lifetime. First measurements of these parameters at injection and flattop have been conducted. Detailed simulations are compared to the measurements together with discussions on the measurement limitations.
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WEPC078 |
Non-linear Chromaticity Studies of the LHC at Injection |
2199 |
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- E.H. Maclean, M. Giovannozzi, F. Schmidt, R.J. Steinhagen, E. Todesco, R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland
- R. Bartolini
JAI, Oxford, United Kingdom
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The non-linear chromaticity of the LHC has been studied. Measurements of variation in tune with dp/p on both beams at injection optics are being compared with Q'' and Q''' as calculated with the LHC effective model. This model uses the best currently available measurements of magnetic field harmonics. An attempt is being made to optimize the b4 and b5 pool-pieces corrections in view of the corresponding chromaticity terms.
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WEPO031 |
The Magnetic Model of the LHC during Commissioning to Higher Beam Intensities in 2010-2011 |
2466 |
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- L. Deniau, N. Aquilina, L. Fiscarelli, M. Giovannozzi, P. Hagen, M. Lamont, G. Montenero, R.J. Steinhagen, M. Strzelczyk, E. Todesco, R. Tomás, W. Venturini Delsolaro, J. Wenninger
CERN, Geneva, Switzerland
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The Field Description of the Large Hadron Collider (FiDeL) model is a set of semi-empirical equations linking the magnets behaviours established from magnetic measurements to the magnetic properties of the machine observed through beam measurements. The FiDeL model includes the parameterization of static components such as magnets residual magnetization, persistent currents, hysteresis and saturation as well as the decay and snap-back dynamic components. In the present paper, we outline the relationship between the beam observables (orbit, tune, chromaticity) and the model components during the commissioning to higher beam intensities in 2010-2011, with an energy of 3.5 TeV per beam. The main relevant issues are (i) the operation at 2 A/s and 10 A/s ramp rate and their influence on chromatic correction, (ii) the beta beating and its relation to the knowledge of the resistive quadrupoles transfer functions and (iii) the observed tune decay at injection energy and its possibles origins.
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TUPS026 |
Specification of New Vacuum Chambers for the LHC Experimental Interactions |
1584 |
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- R. Veness, R.W. Assmann, A. Ball, A. Behrens, C. Bracco, G. Bregliozzi, R. Bruce, H. Burkhardt, G. Corti, M.A. Gallilee, M. Giovannozzi, B. Goddard, D. Mergelkuhl, E. Métral, M. Nessi, W. Riegler, J. Wenninger
CERN, Geneva, Switzerland
- N. Mounet, B. Salvant
EPFL, Lausanne, Switzerland
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The apertures for the vacuum chambers at the interaction points inside the LHC experiments are key both to the safe operation of the LHC machine and to obtaining the best physics performance from the experiments. Following the successful startup of the LHC physics programme the ALICE, ATLAS and CMS experiments have launched projects to improve physics performance by adding detector layers closer to the beam. To achieve this they have requested smaller aperture vacuum chambers to be installed. The first periods of LHC operation have yielded much information both on the performance of the LHC and the stability and alignment of the experiments. In this paper, the new information relating to the aperture of these chambers is presented and a summary is made of analysis of parameters required to safely reduce the vacuum chambers apertures for the high-luminosity experiments ATLAS and CMS.
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