Force field inside the void in complex plasmas under microgravity conditions

Abstract

Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the "trampoline effect"). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force.

Basic Processes in Complex (Dusty) Plasmas: Charging, Interactions, and Ion Drag Force

“…In general, proper choice of the analytical model derived within the BC approximation allows one to get reasonable agreement with experimental results [50,51,53,88,131,134,135] in weakly and moderately collisional plasmas as well as with collisionless numerical simulations [136,137], although in some parameter regimes discrepancies up to a factor ∼ 2 were reported.…”

Impact of collisions on the dust wake potential with Maxwellian and non-Maxwellian ions

“…Due to the presence of micron-sized, highly charged dust particles in addition to electrons, ions and neutrals, these plasmas are endowed with features like self-organization and crystal-structures 5 , low-frequency waves (dust acoustic modes) 6 , or the formation of dust-free structures (voids) in micro-gravity experiments 7 . Complex plasmas have close connections with astrophysics (e.g., dust in planetary rings or cometary tails), low-temperature gas discharge operation (dust inserted into or grown in-situ in gas discharges) 8 , fusion related research (dust generated in plasma-surface interactions) [9][10][11] , warm-dense matter (strong coupling physics) 12,13 as well as the broad regime of material sciences (e.g., defects or wave propagation in dust crystals) 14,15 .…”

Successive Generations of Dust in Complex Plasmas: A Cyclic Phenomenon in the Void Region

“…The assumed mechanism to explain these regions are related to the equilibrium between the inward electrostatic force and the outward ion drag force. Dust voids are still actively studied (see for example [20,21] and references therein). They are experimentally observed in various dusty plasmas both under microgravity conditions or in the laboratory.…”