Kinetic effects in a plasma crystal induced by an external electron beam

Abstract

The kinetic effects on the dust particles are studied experimentally in a plasma crystal locally irradiated by a narrow pulsed electron beam with an energy of 13 keV and a peak current of 4 mA. We observe in the top layer of the plasma crystal the formation of a stable dust flow along the irradiation direction in the first ≈200 ms of the interaction. The dust flow eventually becomes perturbed later in time, with the dust particles having chaotic trajectories as they are still drifting in the beam direction. The speed of the dust flow is mapped in a horizontal plane using the particle image velocimetry technique (PIV). The kinetic energy of the flow and its vorticity are deduced based on the speed vectors provided by PIV. A maximum energy transfer factor ≈0.048 from the electron beam is inferred considering the peak kinetic energy (≈625 eV) of the dust flow. Vortices and tripolar vortices are observed when the dust flow becomes perturbed.