Design optimization of the International Linear Collider Final Focus System with a long L*

This Master's Thesis work has been done in the Aerospace Engineering master's programme framework and carried out at the European Organization for Nuclear Research (CERN). It was conducted under the 500 GeV e-e+ International Linear Collider (ILC) study and focused on the design and performance optimization of the Final Focus System (FFS). The purpose of the final focus system of the future linear colliders (ILC and CLIC) is to demagnify the beam to the required transverse size at the interaction point (IP). The FFS is designed for a flat-beam in a compact way based on a local chromaticity correction which corrects both horizontal and vertical chromaticities simultaneously. An alternative FFS configuration based on the traditional scheme with two dedicated chromatic correction sections for horizontal and vertical chromaticities and a long L * option has been developed. A longer free space between the last quadrupole and the IP allows to place the last quadrupole on a stable ground, with fewer engineering constraints in the detector and could provide a larger detector acceptance. On the other hand a longer L * increases the transport aberrations challenging the optics design. The major tasks of this work are the following: Optimization of alternative FFS based on the traditional design with an L * of 8 meters and a maximum length of 500 meters. Performance of this design is limited by uncorrected higher order aberrations leading to a blow up in the beam size at the IP, especially in the case of the long L * option. The correction of these aberrations is done using particle tracking codes and optimization algorithms to achieve the ILC design luminosity. Tuning procedure simulations are performed on the long free space option of 8 meters for the alternative Final Focus System configuration under realistic magnet misalignments using Beam Based Alignment (BBA) for orbit correction and sextupoles tuning for beam parameters correction. A variety of studies have been carried out on the optimization of the FFS optics for higher order aberrations correction and synchrotron radiation minimization as well as optimization of the L * with a study of the impact of a shorter free space to the IP on beam sizes and luminosity.