1. Beam emittance preservation and tuning in the FCC-ee lepton collider
- Author
-
Doblhammer, Andreas
- Subjects
emittance ,synchrotron radiation ,lattice design ,Physics::Accelerator Physics ,Emittanz ,Beschleunigerdesign ,Lepton Kollisionsbeschleuniger ,Synchrotronstrahlung ,Lepton collider - Abstract
Following the recommendations of the European Strategy Group for High Energy Physics, CERN launched the Future Circular Collider Study (FCC) to investigate the feasibility of large-scale circular colliders for future high energy physics research. In the electron-positron collider of the study, FCC-ee, large synchrotron radiation losses cause the beam to have large local deviations from the design energy. These energy deviations cause orbit o���sets and create the so-called sawtooth e���ect, which causes particles to pass the magnets of the accelerator o���-centre. This in turn causes perturbing magnetic ���elds via the feed-down e���ect. In order to correct the sawtooth e���ect and therefore the feed-down e���ect, the dipole magnets in the machine can be adjusted to the local beam energy in a process called dipole tapering. In the course of this thesis, di���erent dipole magnet tapering scenarios are compared in terms of their e���ectiveness, feasibility and cost. Furthermore, this thesis focuses on tuning the horizontal beam emittance using wigglers. A small value of the beam emittance corresponds to a small beam cross-section, resulting in an increased likelihood of particle collisions and thus a higher luminosity. However, a number of perturbations can cause the beam emittance to deviate from its design value. In order to restore the design emittance, wigglers are implemented in the accelerator lattice. Di���erent wiggler designs will be presented for both decreasing and increasing the value of the horizontal beam emittance. It will be shown, that an emittance decrease and increase by a factor of 10 % with an acceptable increase in synchrotron radiation is possible. The last section of this thesis focuses on chromaticity correction in FCC- ee and its in���uence on the beam emittance. Chromaticity correction schemes with varying numbers of sextupole families are implemented into the FCC-ee lattice. Sextupole strengths are optimized using a downhill simplex algorithm in order to reduce chromaticities up to the fourthorder. Finally, emittance calculations after the application of each correction scheme show, that chromaticity correction schemes can have a signi���cant in���uence on the beam emittance, which should be considered in the design of these correction schemes.
- Published
- 2018
- Full Text
- View/download PDF