Electron cloud studies for heavy-ion and proton machines

Abstract

Electron cloud effects are a known problem in various accelerator facilities around the world. Electron clouds cause instabilities and emittance growth in positron and proton beams as well as in heavy ion beams. Most of the hadron machines experience the build-up of EC due to the multipacting. In LHC and in positron machines production of electrons due to the synchrotron radiation becomes as important as the build-up due to the secondary emission. The main source of seed electrons in heavy ion machines is the residual gas ionization. FAIR facility in Darmstadt will operate with heavy-ion and proton beams. However, the beam parameters are such that the multipacting will start to play a role only for the unconditioned wall with the secondary emission yield more than 1.8. In this paper we study the electron cloud build-up and its effect on the beam stability for FAIR heavy-ion coasting beams. These beams will be used during slow extraction. Electron scattering on the beam ions and its effect on the final neutralization degree and stability is discussed. In this contribution we also present simulation results for LHC and SPS like short proton bunches. We compare the electron cloud induced wake fields obtained using VORPAL and simplified code with 2D Poisson solver. The stopping powers obtained in the simulations are compared with the analytical theory.