Electron Cloud Effects in Cornell Electron Storage Ring Test Accelerator and International Linear Collider Damping Ring

In this paper, the effects of electron cloud are discussed for the ultra low emittance positron beam in Cornell Electron Storage Ring Test Accelerator (Cesr-TA) and the International Linear Collider (ILC) damping ring. We have investigated the electron-cloud instabilities with Cesr-TA which has been operating to experiment for the ILC damping ring with different positron beam energies: 2 and 5 GeV. The electron phase factor, $\omega_{\text{e},y}\sigma_{z}/c$, is given differently to each case. The single-bunch instability is investigated with a simulation based on the strong-strong model by using the simplified lattice. The threshold densities obtained by simulations agree with the predicted values within a factor 1.3. We investigate the effects of the bunch-by-bunch feedback of about 50 turns and non-zero dispersion. The simulation results show that the feedback system suppresses the dipole motion and increases the threshold density in 2 GeV case, but is less effective in 5 GeV case. The threshold densities are degraded with non-zero dispersion in both cases, but the rates of degradation appear differently. We discuss an incoherent emittance growth using the realistic lattice model for Cesr-TA. Below the threshold, the incoherent emittance growth may not be serious in Cesr-TA and the ILC damping ring.