Author: Johannesson, S.
Paper Title Page
THBP31 Electron Cloud Effects in the CERN Accelerators in Run 3 538
 
  • L. Mether, H. Bartosik, L. Giacomel, G. Iadarola, S. Johannesson, I. Mases Solé, K. Paraschou, G. Rumolo, L. Sabato, C. Zannini, E. de la Fuente
    CERN, Meyrin, Switzerland
  • S. Johannesson
    EPFL, Lausanne, Switzerland
 
  Several of the machines in the CERN accelerator complex, in particular the Large Hadron Collider (LHC) and the Super Proton Synchrotron (SPS), are prone to the build-up of electron clouds. Electron cloud effects are observed especially when the machines are operated with a 25 ns bunch spacing, which has routinely been used in the LHC since the start of its second operational run in 2015. After the completion of the LHC Injectors Upgrade program during the latest long shutdown period, the machines are currently operated with unprecedented bunch intensity and beam brightness. With the increase in bunch intensity, electron cloud effects have become one of the main performance limitations, as predicted by simulation studies. In this contribution we present the experimental observations of electron cloud effects since 2021 and discuss their implications for the future operation of the complex.  
DOI • reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP31  
About • Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 23 October 2023
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THBP10 A Linearized Vlasov Method for the Study of Transverse e-Cloud Instabilities 462
 
  • S. Johannesson, M. Seidel
    EPFL, Lausanne, Switzerland
  • G. Iadarola
    CERN, Meyrin, Switzerland
 
  Using a Vlasov approach, electron cloud driven instabilities can be modeled to study beam stability on time scales that conventional Particle In Cell simulation methods cannot access. The Vlasov approach uses a linear description of electron cloud forces that accounts for both the betatron tune modulation along the bunch and the dipolar kicks from the electron cloud. Forces from electron clouds formed in quadrupole magnets as well as dipole magnets have been expressed in this formalism. In addition, the Vlasov approach can take into account the effect of chromaticity. To benchmark the Vlasov approach, it was compared with macroparticle simulations using the same linear description of electron cloud forces. The results showed good agreement between the Vlasov approach and macroparticle simulations for strong electron clouds, with both approaches showing a stabilizing effect from positive chromaticity. This stabilizing effect is consistent with observations from the LHC.  
poster icon Poster THBP10 [4.059 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP10  
About • Received ※ 26 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 14 October 2023
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