Author: Amorim, D.
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THPAB040 Destabilising Effect of Linear Coupling in the LHC 3791
 
  • L.R. Carver, D. Amorim, N. Biancacci, X. Buffat, K.S.B. Li, E. Métral, B. Salvant, M. Schenk
    CERN, Geneva, Switzerland
 
  During operation in 2015 and 2016, some transverse instabilities were observed when either the coupling (or closest tune approach) C- was large, or when the tunes were moved closer together. This motivated a campaign of simulations on the effect of linear coupling on the transverse stability. Measurements made during operation and with dedicated beam time have been found to confirm the predictions. This paper will detail the results of the linear coupling studies and relate them to operation of the LHC in the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB040  
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THPVA026 Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC 4477
SUSPSIK059   use link to see paper's listing under its alternate paper code  
 
  • M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
 
  The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA026  
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THPAB005 Improvement of the Analytic Vlasov Solver DELPHI 3688
 
  • D. Amorim
    Université Grenoble Alpes, Grenoble, France
  • N. Biancacci, K.S.B. Li, E. Métral
    CERN, Geneva, Switzerland
 
  The simulation code DELPHI is an analytic Vlasov solver which allows to evaluate the beam transverse stability with respect to impedance effects. It allows to perform fast scans over parameters such as chromaticity, damper gain or beam intensity for a given impedance model and particle distribution. In order to improve the simulation code, new longitudinal particle distributions have been implemented. The simulations results obtained with these distributions are compared to theoretical predictions. An additional post-processing of DELPHI's output has also been implemented, allowing to reconstruct the signal seen by head-tail stripline monitors, in particular in presence of bunch-by-bunch damper. The results are compared to theoretical models, to pyHEADTAIL simulations and to measurements performed in the LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB005  
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