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

概要

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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.
2011-02-25