Beam optics calculations for CLIC

This Master's thesis was done in the framework of the Master 2 Grands Instruments program of Université Paris Sud and was conducted at the European Organization for Nuclear Research (CERN). It is dedicated to the Compact LInear Collider (CLIC) beam optics studies for initial energy stage of 380 GeV. The thesis focuses on the Final Focus System (FFS) optics, the very last section of the CLIC Beam Delivery System (BDS). The FFS squeezes the beam strongly at the IP, benefiting from the local chromaticity correction scheme, to reach the target luminosity of $10^{34}$cm$^{-2}$s$^{-1}$ order. Initially, the FFS nominal optics with $\beta^*_y = 100$ $\mu$m was analyzed to identify the possible ways to optimize the lattice. Then the FFS optics was optimized with MadX and MAPCLASS to achieve a smaller vertical IP beta function of $\beta^*_y = 70$ $\mu$m while preserving small nonlinear contributions to the IP beam size. The analysis of such optics in terms of luminosity and energy bandwidth was conducted with PLACET and GUINEA-PIG, with synchrotron radiation and beam-beam effects taken into account. Following the obtained results, possibilities for further optimization of the FFS were identified.