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EPFL

1. Salvant, Benoît. Impedance model of the CERN SPS and aspects of LHC single-bunch stability.

Degree: 2010, EPFL

Upgrades of the CERN particle accelerators complex are planned to increase the potential of physics discovery in the LHC. In this respect, the beam coupling impedances of the SPS and LHC are expected to be among the limitations to the intensity upgrade scheme. In this thesis work, we present a general framework to better understand the impedance of a particle accelerator. In a first step, the impedance of single components are gathered into an impedance model accounting for the whole machine. In order to assess the relevance of this impedance model, its impact on beam dynamics is simulated and can be compared to impedance observables measured with beam. This general framework was applied to compute a more accurate transverse impedance model of the SPS from theoretical models for the 20 kickers and the 6.9 km long beam pipe, as well as time domain electromagnetic simulations of the 106 horizontal and 96 vertical SPS beam position monitors. Comparing HEADTAIL macroparticle simulations to beam-based measurements in the SPS, this transverse impedance model turned out to account for 65% of the vertical impedance measured in the machine and showed in addition that the large negative quadrupolar horizontal impedance of the kickers can be held responsible for the measured positive coherent horizontal tune shift with increasing beam intensity. In the course of implementing this framework, new contributions were brought to the understanding of impedances and wake fields. A more general formula was derived for the longitudinal impedance of a multilayer cylindrical beam pipe. New formulae for the transverse quadrupolar impedances of simple models of kickers were also derived and successfully benchmarked to electromagnetic simulations. In addition, MOSES mode coupling analytical calculations were successfully benchmarked against HEADTAIL macroparticle simulations in predicting a Transverse Mode Coupling Instability at injection in the SPS between azimuthal modes -2 and -3. Finally, new RF bench measurements validated the theory proposed by B. Zotter and E. Métral, thereby confirming that the low frequency transverse impedance of the LHC collimators –, which largely dominates the LHC transverse impedance – is less critical than initially expected. Advisors/Committee Members: Rivkin, Leonid, Métral, Elias.

Subjects/Keywords: BPM, collimator; CST Particle Studio; collective effects; dipolar and quadrupolar impedance contributions; HEADTAIL macroparticle simulations; high intensity beams; single-bunch instabilities; impedance; kicker; LHC; mode coupling; MOSES; plug in modules; SPS; TMCI; wake field; BPM; champs de sillage; collimateur; contributions d'impédance dipolaires et quadripôlaires; couplage entre modes; CST Particle Studio; effets collectifs; faisceaux de particules de haute intensité; impédance; interconnexion; instabilités de paquet unique; kicker; LHC; MOSES; simulations HEADTAIL; SPS

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Salvant, B. (2010). Impedance model of the CERN SPS and aspects of LHC single-bunch stability. (Thesis). EPFL. Retrieved from http://infoscience.epfl.ch/record/142384

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Salvant, Benoît. “Impedance model of the CERN SPS and aspects of LHC single-bunch stability.” 2010. Thesis, EPFL. Accessed December 09, 2019. http://infoscience.epfl.ch/record/142384.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Salvant, Benoît. “Impedance model of the CERN SPS and aspects of LHC single-bunch stability.” 2010. Web. 09 Dec 2019.

Vancouver:

Salvant B. Impedance model of the CERN SPS and aspects of LHC single-bunch stability. [Internet] [Thesis]. EPFL; 2010. [cited 2019 Dec 09]. Available from: http://infoscience.epfl.ch/record/142384.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Salvant B. Impedance model of the CERN SPS and aspects of LHC single-bunch stability. [Thesis]. EPFL; 2010. Available from: http://infoscience.epfl.ch/record/142384

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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