Simulation of Ep Instability for a Coasting Proton Beam in Circular Accelerators

Instabilities for a coasting proton beam interacting with electron cloud are discussed. The electron sources are roughly classified into two categories reflecting their initial conditions: that is, the electrons produced at the chamber surface and/or at the beam position. If the beam is stable, it forms a Coulomb static potential around itself. Electrons produced near the beam position are trapped by the potential, while those produced at the chamber surface absorbed after once approaching the beam. We discuss the instability for the two cases in which electrons are produced at chamber and at beam position. The density of electrons are quite different according which initial condition. We notice that the production rate of electrons is important rather than the electron density.