Dust as probes: Determining confinement and interaction forces

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Date
2020-10Author
Hartmann, Peter
Rosenberg, Marlene
Juhasz, Z.
Matthews, Lorin
Sanford, Dustin
Vermillion, Katrina
Reyes, Jorge
Hyde, Truell
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Show full item recordAbstract
The PK-4 system is a micro-gravity dusty plasma experiment currently in operation on-board
the International Space Station. The experiment utilizes a long DC discharge in neon or argon
gases. We apply our 2D particle-in-cell with Monte Carlo collisions discharge simulation to
compute local plasma parameters that serve as input data for future dust dynamics models.
The simulation includes electrons, Ne+ ions, and Ne^m metastable atoms in neon gas and their
collisions at solid surfaces including secondary electron emission and glass wall charging. On
the time scale of the on-board optical imaging, the positive column appears stable and
homogeneous. On the other hand, our simulations show that on microsecond time scales the
positive column is highly inhomogeneous: ionization waves with phase velocities in the range
between 500 m s−1 and 1200 m s−1 dominate the structure. In these waves, the electric field
and charged particle densities can reach amplitudes up to 10 times of their average value. Our
experiments on ground-based PK-4 replica systems fully support the numerical findings. In the
experiment, the direction of the DC current can be alternated, which has been found to favor
dust particle chain formation. We discuss possible mechanisms for how the highly oscillatory
plasma environment contributes to the dust particle chain formation.