Author: Carver, L.R.
Paper Title Page
MOP2WA03 Experiments and Theory on Beam Stabilization with Second-Order Chromaticity 32
 
  • M. Schenk, X. Buffat, L.R. Carver, K.S.B. Li, E. Métral
    CERN, Geneva, Switzerland
  • A. Maillard
    ENS, Paris, France
 
  This study reports on an alternative method to generate transverse Landau damping to suppress coherent instabilities in circular accelerators. The incoherent betatron tune spread can be produced through detuning with longitudinal rather than transverse action. This approach is motivated by the high-brightness, low transverse emittance beams in future colliders where detuning with transverse amplitude will be less effective. Detuning with longitudinal action can be introduced with a radio frequency (rf) quadrupole, or similarly, using second-order chromaticity. The latter was enhanced in the Large Hadron Collider (LHC) at CERN and experimental results on single-bunch stabilization are briefly recapped. The observations are interpreted analytically by extending the Vlasov formalism to include nonlinear chromaticity. Finally, the newly developed theory is benchmarked against circulant matrix and particle tracking models.  
slides icon Slides MOP2WA03 [3.374 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA03  
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MOP2WA05 Simulation and Measurement of the TMCI Threshold in the LHC 43
 
  • D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, L.R. Carver, E. Métral
    CERN, Geneva, Switzerland
 
  The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*1011 protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case.  
slides icon Slides MOP2WA05 [4.729 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA05  
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