Author: Métral, E.
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MOPOTK062 Numerical Calibration of the Bead-Pull Setup for Beam Coupling Impedance Evaluation 607
 
  • D.M.F. El Dali, E. Métral, C. Zannini
    CERN, Meyrin, Switzerland
  • G. De Michele, S. Fanella
    AVO-ADAM, Meyrin, Switzerland
 
  The bead-pull method is a commonly used electromagnetic field measurement technique exploited to tune a radiofrequency cavity to achieve design specifications. The frequency of a resonant cavity is perturbed by inserting a metallic or dielectric bead. For a given electromagnetic field, the amplitude of the perturbation depends only on the geometry of the perturbing object. Therefore, the calibration of the bead can be done in different resonant structures without loss of generality. In this paper, a method to perform an accurate calibration of the bead with electromagnetic simulations is proposed. Compared to the common practice of measuring a reference cavity, the flexibility given by the simulation method to study different bead shapes and sizes could be advantageous to optimize the measurement setup. A calibrated bead-pull setup allows to quantify the electric field and, therefore, the shunt impedance of the resonant modes of the cavity. As experimental benchmark, the beam coupling impedance measured with the calibrated bead-pull setup is compared with electromagnetic simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK062  
About • Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 20 June 2022
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WEPOPT009 Operational Scenario of First High Luminosity LHC Run 1846
 
  • R. Tomás García, G. Arduini, P. Baudrenghien, R. Bruce, O.S. Brüning, X. Buffat, R. Calaga, F. Cerutti, R. De Maria, J. Dilly, I. Efthymiopoulos, M. Giovannozzi, P.D. Hermes, G. Iadarola, O.R. Jones, S. Kostoglou, E.H. Maclean, N. Mounet, E. Métral, Y. Papaphilippou, S. Redaelli, G. Sterbini, H. Timko, F.F. Van der Veken, J. Wenninger, M. Zerlauth
    CERN, Meyrin, Switzerland
 
  A new scenario for the first operational run of the HL-LHC era (Run 4) has been recently developed to accommodate a period of performance ramp-up to achieve an annual integrated luminosity close to the nominal HL-LHC design. The operational scenario in terms of beam parameters and machine settings, as well as the different phases, are described here along with the impact of potential delays on key hardware components.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT009  
About • Received ※ 19 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 09 July 2022
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WEPOTK062 Intrabunch Motion with Both Impedance and Beam-Beam Using the Circulant Matrix Approach 2209
 
  • E. Métral, X. Buffat
    CERN, Meyrin, Switzerland
 
  In high-intensity high-brightness circular colliders such as the CERN LHC, coherent beam-beam effects and impedance cannot be treated independently. Coherent beam-beam dipole modes can couple with higher order head-tail modes and lead to the transverse mode coupling instability of colliding beams. This mechanism has been analysed in detail in the past through the eigenvalues, which describe the evolution of the beam oscillation mode-frequency shifts. In this contribution, the transverse mode coupling instability of colliding beams is studied using the eigenvectors, which describe the evolution of the intrabunch motion. As this instability exhibits several mode couplings and mode decouplings, the evolution of the intrabunch motion reveals quite some interesting features (such as a propagation of the traveling-wave not only from the head to the tail but also from the tail to the head and similar intrabunch signals for some mode coupling and mode decoupling), which are compared to past predictions in the presence of impedance only.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK062  
About • Received ※ 07 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 03 July 2022 — Issue date ※ 06 July 2022
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WEPOTK063 A Wireless Method to Obtain the Impedance From Scattering Parameters 2213
 
  • C. Antuono, M. Migliorati, E. Métral, C. Zannini
    CERN, Meyrin, Switzerland
  • M. Migliorati, A. Mostacci
    LNF-INFN, Frascati, Italy
  • A. Mostacci
    Sapienza University of Rome, Rome, Italy
 
  The coaxial wire method is a common and appreciated choice to assess the beam coupling impedance of an accelerator element from scattering parameters. Nevertheless, the results obtained from wire measurements could be inaccurate due to the presence of the stretched conductive wire that artificially creates the conditions for the propagation of a Transverse ElectroMagnetic (TEM) mode. The aim of this work is to establish a solid technique to obtain the beam coupling impedance from electromagnetic simulations, without modifications of the device under test. In this framework, we identified a new relation to get the resistive wall beam coupling impedance of a circular chamber directly from the scattering parameters and demonstrated that it reduces to the exact theoretical expression. Furthermore, a possible generalization of the method to arbitrary cross section geometries has been studied and validated with numerical simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK063  
About • Received ※ 07 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 20 June 2022  
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THPOMS048 Challenge Based Innovation "Accelerators for the Environment" 3077
 
  • N. Delerue
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • P. Burrows
    JAI, Oxford, United Kingdom
  • R. Holland, L. Rinolfi
    ESI, Archamps, France
  • E. Métral, M. Vretenar
    CERN, Meyrin, Switzerland
 
  Funding: This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730.
We present an initiative to foster new ideas about the applications of accelerators to the Environment. Called "Challenge Based Innovation" this initiative will gather four teams each of six master-level students each coming from different academic backgrounds. As part of the EU-funded I.FAST project (Innovation Fostering in Accelerator Science and Technology), they will gather during 10 days in Archamps near CERN to receive high level lectures on accelerators and the environment and to brainstorm on possible new applications of accelerators for the environment. At the end of the gathering, they will present their project at CERN to a jury made of experts.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS048  
About • Received ※ 09 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 01 July 2022
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