Ground motion in LEP and LHC

The subject ofground motion has been introduced in the field of accelerator physics by G. Fischer l , 2 of SLAC about 10 years ago.At that moment several colliders, linear and circular, are at various stages in the design phase.Their common characteristics are large machine dimensions and extremely small beam sizes.The extreme dimensions make these colliders more prone to ground motion effects while the minute beam size increases their sensitivity.The object of this paper is to report on the results obtained with a dedicated beam position monitor, concerning ground motion effects on the LEP beams.It starts with some properties of ground vibrations which are relevant to the observation of the phenomenon in LEP.The results of the observations will be presented both at the betatron frequencies and at very low frequencies.They are compared with published data to check the plausibility of the hypothesis that ground motion is indeed the primary cause of the observed signals.Finally, a discussion on the influence of the effect on the LHC beams is presented.