The electron cloud instability of the LHC beam in the CERN SPS

The electron cloud induced by the LHC beam in the SPS occurs mainly in the dipoles and it is responsible for strong transverse instabilities. In the horizontal plane a coupled bunch mode instability develops in a few tens of turns at injection. Tune shift measurements, mode number and phase space analyses have been performed at different energies and provide information about the electron cloud distribution and its dynamics. In the vertical plane a single bunch head-tail like instability occurs. The equivalent ´electron-cloud wake field´ is inferred from the analysis of the head-tail motion of the bunches of the LHC beam train.