Laboratory Experiments

Compared to similar experiments in other fields such as colloids, granular materials or fluids, dusty plasmas have three very convenient and advantageous properties which result in a superb experimental accessibility:

  • Even micron-sized dust particles can be observed with the naked eye, given a proper illumination of the dust (usually done with lasers). Hence, cameras can be used for the observation of individual particles.
  • Although the dust particles have a high electric charge (typically 1000 to 10000 elementary charges), their charge-to-mass ratio is quite small due to their heavy mass (compared to ions and electrons). As a consequence, the dynamics of the dust particles are very slow with  that the dust particles move quite slow, with dynamical phenomena happening on the scale of some milliseconds to seconds. Hence, the full dust dynamics can be captured with cameras providing some 100 to 1000 fps.
  • Due to the electric repulsion between the like-charged dust particles, the inter-particle distance is very large compared to the particle size (typically at least a factor of 100 larger).  Dust clouds are therefore „transparent“ (in most experimental situations)
Spherical cluster of about 1000 dust particles („Yukawa ball“)

The scientific complexity paired with the convenient experimental acces makes dusty plasmas an ideal tool for fundamental research. Besides the appilications in space or technological plasmas, dusty plasmas provide the opportunity to study physical concepts like strongly coupled Coulomb systems or non-linear wave dynamics. Investigations of dynamical phenomena are further encouraged by the fact that the dust particles are embedded in a gaseous plasma environment, where the gas friction is very low, resulting in rich and only weakly damped dynamics (in contrast to colloidal suspensions – small particles suspended in liquids, which experience much more frictional damping).

trajectories of dust particles in a dust density waves
self-excited dust density waves under weightlessness (image size: some cm)
self-excited vortex (long-time exposure)