Simulated Emittance Growth due to Electron Cloud for SPS and LHC

The emittance growth caused by an electron cloud is simulated by the HEADTAIL code with conducting boundary conditions. Under some conditions the simulation results may depend on the number of beam-cloud interaction points, the phase advance between them and the number of macroparticles used to represent beam and cloud. Simulations include a transverse feedback system and, optionally, a large chromaticity, as employed in actual SPS operation. Simulation results for the SPS can be compared with observations, and the emittance growth in the LHC is computed as a function of average electron 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.