Author: Fartoukh, S.D.
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TUPVA009 Multiparametric Response of the LHC Dynamic Aperture in Presence of Beam-Beam Effects 2051
 
  • D. Pellegrini, F. Antoniou, S.D. Fartoukh, G. Iadarola, Y. Papaphilippou
    CERN, Geneva, Switzerland
 
  We performed extended simulations of LHC dynamic aperture (DA) in the presence of beam-beam effects in the weak-strong approximation, evaluating the contributions of parameters such as: tunes, optics, bunch intensity, crossing angle, emittance, chromaticity and current in the Landau octupoles. Here we present a summary of these studies, giving an overview of the amplitude of the LHC operational space and pointing out the remaining margins for mitigation of instabilities. These studies supported the actions deployed during the 2016 run of the LHC, which aimed at maximising its performances. Examples of such actions are the switch to lower emittance beams, the reduction of crossing angle and tune trims. More recently, DA scans have been used to help the definition of the operational scenarios for the 2017 run. Additional room for improvements, for instance by deploying crossing angle levelling, will be explained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA009  
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TUPVA010 Multiparametric Response of the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects 2055
 
  • D. Pellegrini, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou
    CERN, Geneva, Switzerland
 
  We performed extended simulations of HL-LHC dynamic aperture in the presence of beam-beam effects in the weak- strong approximation, evaluating the contributions of param- eters such as: bunch intensity, crossing angle, chromaticity, current in the Landau octupoles and multipole errors. From the beam dynamics point of view, the main differ- ence between the LHC (until 2017) and the HL-LHC is the deployment of the achromatic telescopic squeezing (ATS) optics, allowing not only for a smaller '' reach, but also modifying the phase advances between the lattice correctors (sextupoles, octupoles) and the main IPs, and increasing the peak ' functions in the arcs. These correctors become therefore more efficient for the chromatic correction, but also a mitigation of the beam-beam long range interactions using the Landau octupoles is enabled, resulting in a possible reduction of the normalised crossing angle. The limits have been investigated in a tracking simulation campaign aimed at exploring the operational space for the HL-LHC and two possible options for luminosity levelling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA010  
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TUPVA115 Progress with Long-Range Beam-Beam Compensation Studies for High Luminosity LHC 2358
 
  • A. Rossi, O. Aberle, J. Albertone, A. Bertarelli, C.B. Boccard, F. Carra, G. Cattenoz, Y. Delaup, S.D. Fartoukh, G. Gobbi, J. Lendaro, Y. Papaphilippou, D. Perini, S. Redaelli, H. Schmickler, C. Zanoni
    CERN, Geneva, Switzerland
  • A.M. Barnyakov, A.E. Levichev, D.A. Nikiforov
    BINP SB RAS, Novosibirsk, Russia
  • M. Fitterer, A.S. Patapenka, G. Stancari, A. Valishev
    Fermilab, Batavia, Illinois, USA
 
  Long-range beam-beam (LRBB) interactions can be a source of emittance growth and beam losses in the LHC during physics and will become even more relevant with the smaller '* and higher bunch intensities foreseen for the High Luminosity LHC upgrade (HL-LHC), in particular if operated without crab cavities. Both beam losses and emittance growth could be mitigated by compensat-ing the non-linear LRBB kick with a correctly placed current carrying wire. Such a compensation scheme is currently being studied in the LHC through a demonstration test using current-bearing wires embedded into col-limator jaws, installed either side of the high luminosity interaction regions. For HL-LHC two options are considered, a current-bearing wire as for the demonstrator, or electron lenses, as the ideal distance between the particle beam and compensating current may be too small to allow the use of solid materials. This paper reports on the ongoing activities for both options, covering the progress of the wire-in-jaw collimators, the foreseen LRBB experiments at the LHC, and first considerations for the design of the electron lenses to ultimately replace material wires for HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA115  
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WEPIK030 Experimental Validation of the Achromatic Telescopic Squeezing Scheme at the LHC 2992
 
  • S.D. Fartoukh, R. Bruce, F.S. Carlier, J.M. Coello de Portugal, A. Garcia-Tabares, E.H. Maclean, L. Malina, A. Mereghetti, D. Mirarchi, T. Persson, M. Pojer, L. Ponce, S. Redaelli, B. Salvachua, P.K. Skowroński, M. Solfaroli, R. Tomás, D. Valuch, A. Wegscheider, J. Wenninger
    CERN, Geneva, Switzerland
 
  The Achromatic Telescopic Squeezing (ATS) [1] scheme offers new techniques to deliver unprecedentedly small beam spot size at the interaction points of the ATLAS and CMS experiments of the LHC, while perfectly controlling the chromatic properties of the corresponding optics (linear and non-linear chromaticities, off-momentum beta-beating, spurious dispersion induced by the crossing bumps). The first series of beam tests with ATS optics were achieved during the LHC Run I (2011/2012) for a first validation of the basics of the scheme at small intensity. In 2016, a new generation of more performing ATS optics was developed and more extensively tested in the machine, still with probe beams for optics measurement and correction at β*=10 cm, but also with a few nominal bunches to establish first collisions at nominal β* (40 cm) and beyond (33 cm), and to analysis the robustness of these optics in terms of collimation and machine protection. The paper will highlight the most relevant and conclusive results which were obtained during this second series of ATS tests.
[1] S. Fartoukh , Phys. Rev. ST Accel. Beams 16, 111002
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK030  
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