Diffuse plasma effects on the ion-hose instability

The transverse stability of a relativistic electron beam focused by an ion channel in the presence of a diffuse background plasma is investigated. The linear behavior of the ion-hose and electron two-stream instabilities is treated analytically using a spread-mass model for the beam and ion channel and a cold-fluid model for the plasma. The electron two-stream instability is found to be quite weak. As the plasma neutralization radius approaches the beam radius, the ion-hose growth rate is reduced up to 50% before the model’s assumptions break down. Particle-in-cell simulations confirm the linear analytic theory and show that the electron two-stream instability can saturate nonlinearly with little beam emittance growth.