Real-timefeedback on beam parameters

Traditionally, tight beam parameter stability requirements were most pronounced for light sources and lepton colliders but have now become increasingly important for present and future hadron accelerator operation, not only for performance but also for reasons of machine protection, as recent improvements have led to significantly increased stored beam energies. In the latest generation machines, performance depends critically on the stability of the beam. In order to counteract disturbances due to magnetic imperfections, misalignments, ground motion, temperature changes and other dynamic effects, fully automated control of the key beam parameters – orbit, tune, coupling, chromaticity and energy – becomes an increasingly important aspect of accelerator operation. This contribution presents an overview of beam-based feedback systems, their architecture, performance limitations and design choices involved.