• J. Pfingstner, D. Schulte
  CERN, Geneva
• M. Hofbaur
  UMIT, Hall in Tirol

One of the major challenges of the CLIC main linac is the preservation of the ultra-low beam emittance. The dynamic effect of ground motion would lead to a rapid emittance increase. Orbit feedback systems (FB) have to be optimized to efficiently attenuate ground motion (disturbance), in spite of drifts of accelerator parameters (imperfect system knowledge). This paper presents a new FB strategy for the main linac of CLIC. It addresses the above mentioned issues, with the help of an adaptive control scheme. The first part of this system is a system identification unit. It delivers an estimate of the time-varying system behavior. The second part is a control algorithm, which uses the most recent system estimate of the identification unit. It uses H2 control theory to deliver an optimal prediction of the ground motion. This approach takes into account the frequency and spacial properties of the ground motion, as well as their impact on the emittance growth.