Ground motion studies for large future linear colliders

A future large accelerator, such as a TeV linear collider, should have an extremely small emittance to give the required luminosity. Precise alignment of machine components is essential to prevent emittance dilution. The ground motion spoils alignment of the accelerator elements and results in emittance growth. This paper discusses ground motion and its effect on the main linac. The ground motion in the frequency range of seismic vibration is mostly coherent in the related accelerator. However the incoherent diffusive or Brownian like motion may become dominant for a frequency region less than seismic vibration. This paper starts from the power spectrum of the ATL model then shows typical parameters of main linacs and considers measured data including excavated effects.