Simulation studies of controlled longitudinal emittance blow-up in the HL-LHC era

During the acceleration ramp of the LHC, single bunches would lose Landau damping lon- gitudinally if their bunch emittance was preserved. Thus the LHC, by design, indispensably requires a controlled longitudinal emittance blow-up during the ramp to counteract loss of Landau damping. Controlled emittance blow-up has been operationally used since the start- up of the machine for nominal bunch intensities. The future High-Luminosity LHC project aims at doubling this intensity, and per se, it is not clear whether the presently operational method for the blow-up will still work at those intensities. In the past, simulation studies were conducted for nominal intensities and neglecting collective effects. In this thesis, we first review the threshold of loss of Landau damping in simulations and then we study blow-up for present and future beam intensities with collective effects. This is a computationally challenging task, even for single bunches, as it requires simulating the whole acceleration ramp of LHC, which is fourteen million turns long.