Shown below is an animated gif from a simulation of a pure electron plasma in thermal equilibrium in a modified Penning-Malmburg trap. Radial confinement is provided by a uniform axial magnetic field. The first frame shows electric field equipotentials in the empty trap (no electrons). The second and following frames show the added electron cloud growing from low density to the confinement limit at constant temperature (5% of endcap potential energy).
The trap potential is made visible by a family of equipotential surfaces (95%, 90%, .. 5%) of the endcap potential. In some cases one equipotential lying close to the plasma potential is omitted for clarity.
The total charge density is displayed by a false color plot, with logarithmic scale (a factor e between colors: magenta = 100% of maximum density, blue = 37%, cyan = 13.5%, ..). Densities below red = 0.7% are not shown.
The inset shows the radial density profile and its radial derivative. As the density increases the flattening of the central density signals the onset of the Debye screening by which the plasma shields its interior from the trap electric field.