Optics Corrections and Stabilization Methods for Particle Accelerators

Licentiate thesis, 2013

The discovery of a Higgs-like particle is the result of excellent performance of both the LHC (Large Hadron Collider) and its detectors. A significant part of the success can be attributed to the excellent control of the optics in the accelerator. In this thesis the methods used to correct the optics functions are presented. The corrections of the 2012 nominal optics resulted in an unprece- dented low β-beat for a hadron collider. These results, together with the results from the corrections of the high-β ∗ optics, are presented in this thesis. Following the discovery of the Higgs-like particle in the LHC there is a de- mand for precise measurements of its properties in a lepton collider. CLIC (Compact Linear Collider), an electron-positron collider aiming at collision en- ergies up to 3 TeV, is one of the candidates. The acceleration in CLIC relies on a two-beam acceleration scheme where one of the beams, referred to as the Drive Beam, is decelerated while transferring its energy to the Main Beam. This scheme puts tight constraints on the Drive Beam stability in terms of beam current, phase and bunch length. In CTF3 (CLIC Test Facility 3) the mechanisms behind the observed drifts of these parameters have been studied in detail. The findings have shown that these drifts are mainly linked to varia- tions in the RF (Radio Frequency). A feedback to mitigate the RF-amplitude fluctuations has been implemented and is described in detail. Working together with a dedicated energy feedback it reduces the energy variation by almost a factor 3. Together with precise machine tuning this has resulted in a beam current stability very close to the CLIC requirement. The beam phase stabil- ity is improved through a feedback operating on the two first klystrons in the CTF3 injector. These, studies together with the implemented feedbacks, are presented in this thesis. The two-beam acceleration at the nominal CLIC gradient of 100 MV/m and above has been demonstrated in CTF3. These results, and other recent achievements in CTF3, are presented in this thesis.