Cathode physics in non-neutral plasmas

V. Gorgadze (UCB-Physics)

Single species plasmas, such as particle beams and nonneutral plasmas,
share many basic physics phenomena.  Theoretical and numerical
studies are conducted for nonneutral plasma traps that are of both of
a fundamental nature and have analogs in beam physics: the self-field
effects during current injection into traps and multi-beam
instability.

The process of injection is shown to be a much richer nonlinear
phenomena than previously imagined. Enhanced trapping can occur due to
inhomogeneous two-stream instability and virtual cathode
formation. Estimates of instability threshold and critical current for
these phenomena are presented.  An approximate method for studying the
influence of self-fields during the initial acceleration near the
cathode was developed and shown to be in agreement with numerical
simulation. The analysis included finite radial effects and showed
that step-profile beams suffer greater distortion than Gaussian beams
during the initial acceleration.