ORBIT FEEDBACK CONTROL FOR THE LHC Prototyping at the SPS

The Large Hadron Collider (LHC) is the next generation proton collider that is presently built at CERN. The LHC will be installed in the former LEP (Large Electron Positron Collider) tunnel. The presence of a high intensity beam in an environment of cryogenic magnets requires an excellent control of particle losses from the beam. Eventually the performance of the LHC may be limited by the ability to control the beam losses. The performance of the LHC cleaning system depends critically on the beam position stability. Ground motion, field and alignment imperfections and beam manipulations may cause orbit movements. The role of the future LHC Orbit Feedback System is the minimisation of closed orbit perturbations by periodically measuring and steering the transverse beam position back to its reference position. This diploma thesis focuses on the design and prototyping of an orbit feedback system at the SPS. The design is based on a separation of the steering problem into space and time. While the correction in space is done by a standard orbit correction algorithm, the correction in time is done by a PID controller that minimises steady state errors and improves the response time of the system. The design was experimentally verified at the SPS and showed a good feedback performance. Although the concrete design parameters are specific to the SPS, we believe that the design can be ported to the LHC. This thesis summarises the design, prototyping and results of the SPS feedback system. It points out necessary improvements for the next version of the feedback system.