Author: Arsenyev, S.
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MOPMF029 FCC-hh transverse impedance budget 149
 
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  
  Contributions of different machine elements of the proposed Future Circular Collider (FCC-hh) impedance budget are calculated based on beam stability considerations. For each element (the beamscreen, the collimators, etc), effective impedances are calculated at the injection energy and at the collision energy for considered instabilities. The considered instabilities include the transverse coupled bunch instability (TCBI) and the transverse mode coupling instability (TMCI). Limitations to each total effective impedance are estimated and the critical points in the impedance budget are determined.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF029  
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MOPMF030 Broadband Impedance of Pumping Holes and Interconnects in the FCC-hh Beamscreen 153
 
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
  
  In the proposed Future Circular Collider (FCC-hh) pumping holes and interconnects between sections of the beamscreen can be sources of unwanted broadband impedance, potentially leading to the transverse mode coupling instability (TMCI). The pumping holes pose a greater challenge to the impedance calculation due to their small contribution per hole. Unlike for the Large Hadron Collider (LHC), analytical methods cannot be applied due to the complex beamscreen geometry and the greater size of the holes. Instead, two computational methods are used and compared to each other. For the interconnects, the impedance due to a sophisticated system of tapers is also estimated using computational methods.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF030  
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MOPMF031 Modelling Wake Impedance of a Rough Surface in Application to the FCC-hh Beamscreen 157
 
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
  
  The inner surface of the future circular collider (FCC-hh) beamscreen is proposed to be laser-treated in order to mitigate the electron cloud build-up. However, the rough structure of the treated surface can result in unwanted impedance increase, potentially leading to the transverse mode coupling instability (TMCI). Three models have been adopted to estimate the wake impedance of a beamscreen with a rough surface. The models use the resistive wall formalism generalized for the case of an arbitrary surface impedance. The results apply to a beamscreen of a circular cross-section with the homogeneously rough inner surface for the case of ultrarelativistic particles. The free parameters of the models were fit into preliminary measurements of the surface resistivity, giving, as a result, a range of the real and the imaginary parts of the wake impedance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF031  
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MOPMF064 High-Energy LHC Design 269
 
  • F. Zimmermann, D. Amorim, S. A. Antipov, S. Arsenyev, M. Benedikt, R. Bruce, M.P. Crouch, S.D. Fartoukh, M. Giovannozzi, B. Goddard, M. Hofer, R. Kersevan, V. Mertens, Y. Muttoni, J.A. Osborne, V. Parma, V. Raginel, S. Redaelli, T. Risselada, I. Ruehl, B. Salvant, D. Schoerling, E.N. Shaposhnikova, L.J. Tavian, E. Todesco, R. Tomás, D. Tommasini, F. Valchkova-Georgieva, V. Venturi, D. Wollmann
    CERN, Geneva, Switzerland
  • J.L. Abelleira, E. Cruz Alaniz, P. Martinez Mirave, A. Seryi, L. van Riesen-Haupt
    JAI, Oxford, United Kingdom
  • A. Apyan
    ANSL, Yerevan, Armenia
  • J. Barranco García, L. Mether, T. Pieloni, L. Rivkin, C. Tambasco
    EPFL, Lausanne, Switzerland
  • F. Burkart
    DESY, Hamburg, Germany
  • Y. Cai, Y.M. Nosochkov
    SLAC, Menlo Park, California, USA
  • G. Guillermo Cantón
    CINVESTAV, Mérida, Mexico
  • K. Ohmi, K. Oide, D. Zhou
    KEK, Ibaraki, Japan
  
  In the frame of the FCC study we are designing a 27 TeV hadron collider in the LHC tunnel, called the High Energy LHC (HE-LHC).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF064  
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MOPMK014 Resistive-Wall Impedance of Insertions for FCC-hh 378
 
  • B. Riemann, S. Khan
    DELTA, Dortmund, Germany
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
  
  Funding: This work is supported by the German Ministry of Education & Research (BMBF, funding code 05P15PERB1) and CERN (reference numbers KE3123, EDMS 1606722).
In this work, transverse and longitudinal resistive-wall impedances for beam pipes in the experiment, injection, extraction and RF systems insertion regions of the Future Hadron-Hadron Collider (FCC-hh) are computed based on contributions from different given cross sections of the surrounding (elliptical) chamber parts along the beam path, their temperature-dependent conductivities, and optical functions. An emphasis is placed on the behaviour of transverse impedance in the main experimental regions (A and G), where maximum beta values of 104 to 105 m occur in dependence of the operation mode respectively lattice configuration. Main contributions to the transverse and longitudinal impedance budget are identified, and possibilities of reducing them are discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK014  
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THPAF074 Landau Damping Studies for the FCC: Octupole Magnets, Electron Lens and Beam-Beam Effects 3150
 
  • C. Tambasco, J. Barranco García, T. Pieloni, L. Rivkin
    EPFL, Lausanne, Switzerland
  • S. Arsenyev, X. Buffat, D. Schulte
    CERN, Geneva, Switzerland
  
  Funding: This work is supported by the Swiss State Secretariat for Education, Research and Innovation SERI.
Stability studies for the FCC-hh operational cycle are explored using Landau octupoles and electron lenses alone and in the presence of long-range as well as head-on beam-beam effects. Pros and cons of the various methods are compared and an optimum operational scenario to guarantee the maximum stability is proposed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF074  
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