ACTIVE VIBRATION ISOLATION SYSTEM FOR CLIC FINAL FOCUS

Abstract

With pinpoint accuracy, the next generation of Linear Collider such as CLIC will collide electron and positron beams at a centre of mass energy of 3 TeV with a desired peak luminosity of 2*10 34 cm -2 s -1 . One of the many challenging features of CLIC is its ability to collide beams at the sub-nanometer scale at the Interaction Point (IP). Such a high level of accuracy could only be achieved by integrating Active Vibration Isolation systems (AVI) upstream of the collision to prevent the main source of vibration: Ground Motion (GM). Complementary control systems downstream of the collision (Interaction Point FeedBack (IPFB), Orbit FeedBack (OFB)) allow low frequency vibration rejection. This paper focuses on a dedicated AVI table designed for the last focusing quadrupole (QD0) where the specifications are the most stringent. Combining FeedForward (FF) and FeedBack (FB) techniques, the prototype is able to reduce GM down to 0.6 nm RMS(4Hz) experimentally without any load. These performances couldn’t be achieved without cutting edge-technology such as sub-nanometer piezo actuators, ultra-low noise accelerometers and seismometers and an accurate guidance system. The whole AVI system is described in details. Further developments concern the integration of the final focusing magnet above the AVI table, first as part of the simulation with its dynamical model, and finally, as a realistic prototype.