Simulation of Ground Motion Induced Proton Beam Orbit Vibration in Hera

Ground motion induced beam jitter plays an important role for many kinds of accelerators, like future linear colliders, synchrotron radiation sources or storage rings. The resulting beam orbit vibration potentially leads to luminosity degradation in colliding beam facilities due to beam offset at the interaction point and/or emittance growth. The sensitivity of beam orbits to quadrupole motion depends strongly on the correlation length of ground motion at a specific frequency. Quadrupole motion with a correlation length exceeding the betatron wavelength has only little influence on beam jitter [1]. Therefore any simulation of ground motion effects has to take into account not only the power spectrum of motion at a single point but also the coherence properties of ground motion. This paper presents a ground motion simulation model which has been originally developed for linear accelerators [2]. It is based on measured power spectra and coherence properties of ground motion. This model is extended to circular machines in order to simulate ground motion induced beam jitter in the HERA proton ring.