Simulation of ground motion induced beam jitter in the SBLC main linac

To keep the two beams of linear colliders in collision, the beam offset with respect to each other should be significantly below the beam size. To investigate the effect of ground motion on the beam trajectory, a ground motion simulation algorithm has been developed. This code models measurements taken at various laboratory sites and pays special attention to coherence properties of ground motion. Additionally, possible stabilization feedback algorithms are included. The code can be adapted to a broad range of vibration spectra and coherence properties. As a specific application, beam jitter in the main linac of the S-band Linear Collider SBLC has been investigated. The resulting rms beam jitter of σ_y≈1.3 μm corresponds to a luminosity degradation of only 1%. The jitter can be reduced to about 0.45 μm using active stabilization of quadrupole vibrations. This indicates that, with respect to ground vibration, there is significant luminosity upgrade potential for SBLC