Simulation of transverse single bunch instabilities and emittance growth caused by electron cloud in LHC and SPS

The electron cloud may cause transverse single-bunch instabilities in proton beams such as those in the LHC and the CERN SPS.These instabilities and the consequent emittance growth are simulated by the HEADTAIL code with conducting boundary conditions.The sensitivity of the simulation results to several numerical parameters is studied by varying the number of interaction points of the bunch with the cloud, the phase advance between subsequent interaction points and the number of macroparticles used to represent the protons and the electrons.Simulations for the SPS, including a transverse feedback system and a dipole magnetic field, can be used to benchmark the code with machine observations.The effects of a large chromaticity on the instability evolution are investigated for both SPS and LHC, considering various levels of electron cloud density.An attempt is made to extrapolate to low electron densities.We also compare the initial instability rise times with those obtained for an equivalent broadband resonator.