Machine Protection and Beam Quality during the LHC Injection Process

This thesis is concerned with the machine protection system for the LHC injection process, where the intensity of the injected beam is alreay more than one order of magnitude above the equipment damage level. It focuses on a detailed specification, description and performance validation of the protection systems for the transfer from the SPS and the injection into the LHC. Numerical simulations were used to design active (equipment monitoring to ensure correct settings) and passive (collimators and absorbers) protection systems, and to analyze their performance. The simulation methodology was based on two common computer codes: energy deposition simulations were done with FLUKA and particle tracking was done with the tracking module of MAD-X. Realistic machine states were set up for the failure simulations including geometrical and optical mismatch, orbit tolerances, mechanical tolerances, power converter ripples, misalignment of elements and trajectory correction. The equipment damage limit was derived and checked experimentally. The required protection settings, expected beam loss levels and achievable overall protection level for the injection process were evaluated with these simulation techniques. Beam quality aspects for the injected beam were also treated, quantifying the expected emittance degradation during the injection process. The results of the commissioning of one of the two transfer lines between the SPS and the LHC are summarized, including an experiment to align a collimator jaw with beam. The results obtained demonstrate that the LHC can be fully protected with the proposed systems, and provide detailed specifications for the surveillance, interlocking and passive protection device performance requirements.