Dust crystal interaction with plasma flows

Summary form only given. A novel experiment is proposed to study the interaction between a dust crystal formed in a low ionized rf plasma (n
e
≈ 10
¹⁵
m
⁻³
) with room temperature ions (≈ 0.025 eV) [1, 2] and an incident plasma flow with a few orders of magnitude higher density (n
e
≈10
¹⁷
–10
¹⁸
m
⁻³
), ions with temperature ≈ 1 eV and drift velocity of the order of ≈ 10 km/s. The higher density plasma flow is produced inside a miniature coaxial plasma gun powered by a capacitor bank [3]. Of major interest here is the dynamics of the plasma crystal as the density of the charged particles increases. The Debye length is reduced and therefore the electrostatic coupling between the dust particles is expected to be weaker. At the same time the electrical charge on the micron-size dust particles varies rapidly [4]. Real-time monitoring with a high-speed camera of particle trajectories can provide direct information on dust charging, dust-dust and dust-plasma flow interactions. Additionally, the generated plasma flow can create dust wakes in the direction of the flow. A vertical wake structure already exists in the steady crystal residing in the rf plasma sheath and it affects mostly the lower layers of the dust crystal, as ions stream through the sheath to the electrode. For a plasma flow parallel with the horizontal dust layers, wakes could be formed in the horizontal direction of the crystal as well. This can allow the creation of a plasma crystal with a double structure of vertical and horizontal wake potential wells, which can lead to the observation of new interesting phenomena.