Interaction point feedback design and integrated simulations to stabilize the CLIC final focus

The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the offset position between the beams. Sensitive to ground motion (GM), the beam needs to be stabilized to unprecedented requirements. Different Beam Based Feedback (BBF) algorithms such as Orbit Feedback (OFB) and Interaction Point Feedback (IPFB) have been designed. This paper focuses on the IPFB control which could be added to the CLIC baseline. IPFB control has been tested for different GM models in presence of noises or disturbances and it uses digital linear control with an adaptive loop. The simulations demonstrate that it is possible to achieve the required performances and quantify the maximum allowed noise level. This amount of admitted noises and disturbances is given in terms of an equivalent disturbance on the position of the magnet that controls the beam offset. Due to the limited sampling frequency of the process, the control loop is in a very small bandwidth. The study shows that these disturbances have to be lowered by other means in the higher frequency range.