Breaking the Azimuthal Symmetry- Jumping off-axis or Staying Away from the Axis?

摘要

We performed experiments with electrons in a Malmberg-Penning trap, as well as 2D fluid simulations, and found conditions that lead to off-axis equilibrium slates. We found that unstable initial distributions whose average distance from the axis is larger than about half the wall radius end up in off-axis states. These states consist of a small strong vortex and a large diffuse background, each having about half of the initial charge. We present a simple model showing that for small initial distributions, on-axis solutions maximize the background radius and thus the entropy. For extended initial distributions, no on-axis solutions are available and staying off-axis is necessary for the conservation of angular momentum.