Diocotron instability of a relativistic coaxial multi-ring hollow electron beam

Abstract

The diocotron stability properties of a relativistic coaxial multi-ring hollow electron beam are investigated using a macroscopic cold fluid description based on moment-Maxwell equations. It is found that for a broad range of beam parameters and somewhat more general type beam profiles, the growth rate of instability has a sensitive dependence on fractional charge neutralization, relative position of the rings with conducting wall, and gap-length of the rings. In the case of a sharp boundary density profile, the beam can easily be stabilized by a small fractional charge neutralization with appropriate gap-length. The growth rate can be either enhanced or reduced depending on the position and gap-length of the rings.