A Shaky Road to Subnanometer Beams. NLC Ground Motion, Vibration and Stabilization Studies

Ground motion and vibration can be a limiting factor in the performance of future linear colliders. Investigations of ground motion have been carried out around the world for several decades. In this review, results of recent investigations of ground motion as well as ongoing developments of stabilization methods are presented. 1 GROUND MOTION STUDIES Ground motion can conveniently be divided into 'fast' and 'slow' when studying its effect on a linear collider. Fast motion (f > a few Hz) cannot be adequately corrected by a pulse-to-pulse feedback operating at the repetition rate of the collider and therefore primarily causes beam offsets at the IP. Slow motion can be compensated by feedback and thus results only in beam emittance growth. Another consideration is that the mechanism that produces relative displacements is different (discussed below) for slow and fast motion with a boundary occurring somewhere in a milli-Hz range.