Novel beam-based correction and stabilisation methods for particle accelerators

Precise control of beam optics and beam stability is of critical importance for machine protection and performance of today's high-energy particle accelerators. For the next generation of accelerators, the tolerances are even tighter. This thesis presents new methods and improved techniques to efficiently identify, measure and correct a range of errors in particle accelerators. Circular and linear accelerators have been studied in parallel. The Circular Large Hadron Collider (LHC) collides mostly protons at energies of 6.5 TeV and European Synchrotron Radiation Facility (ESRF) storage ring accelerates electrons to produce synchrotron light. The Compact Linear Collider (CLIC) will provide electron-positron collisions at centre of mass energies up to 3 TeV. In CLIC, a non-colliding beam, referred to as drive beam, generates RF power to accelerate the main beam. LHC's optics measurement scheme was improved, also by studying ESRF. This resulted in significantly improved $\beta$-function measurement, achieving twice the best-documented precision so far. The optics correction algorithm was improved allowing $\beta$-beating in the LHC to systematically reach a level below 1.8% rms. An adiabatic simultaneous 3-dimensional beam excitation, which combines AC-dipoles with RF-frequency modulation, significantly sped up beam optics measurements. The analysis of beam frequency spectra from turn-by-turn data was also made significantly faster, in the LHC by a factor $\sim 300$. These results contributed to LHC's excellent performance beyond its designed targets. They also contributed towards its upgrade the High Luminosity LHC. CLIC has stringent requirements on drive beam stability in terms of beam current, energy and phase. In the CLIC Test Facility 3 (CTF3), a novel algorithm to identify drifts and correlations was developed and applied in a study of drive beam stabilisation. The underlying causes of drifts were found and multiple beam-based feedbacks were developed and commissioned in CTF3, in this way achieving the stability goals. These improvements therefore played a key role in demonstrating the viability of CLIC in terms of drive beam stability.