Ion hose instability of an intense beam with a Bennett profile

Abstract

Summary form only given. A steady-state model has been formulated to describe the propagation of an intense relativistic electron beam into vacuum after passage through a localized plasma. A self-consistent relativistic Vlasov-based equilibrium, which leads to the Bennett radial density profile, has been found for the downstream electron-ion beam. The ion hose instability of this self-pinched beam was examined, with emphasis placed on the equilibrium case in which the ions are cold and stationary and provide total charge neutralization. A simple description of the ion hose instability is given by the rigid beam model. The anharmonic nature of the transverse potential well was investigated by assuming that the beam is composed of many small annular regions with a density given by the Bennett profile. The results indicate that due to phase mixing the maximum growth is considerably reduced and the spectrum of unstable wavelength is broadened, and the instability is shown to be convective rather than absolute. The effects due to an axial velocity spread of the electron beam species were also considered