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Density waves in a cloud of submicron dust particles confined in an rf plasma are examined with respect to their amplitude. The plasma shows a strong inhomogeneity in its densities and the dust particle charge. An ion density gradient appears due to ambipolar diffusion and leads to a dust charge gradient provided by charge depletion. Using dust-density wave frequency and wave number as a diagnostic for the plasma parameters, it is found that the wave amplitude increases or decreases as the wave travels into regions with decreasing or increasing particle charge. The experimental amplitude profile is similar to the theoretical curve predicted by a formula from Singh and Rao. [ABSTRACT FROM AUTHOR]

A dust density wave field is observed in a cloud of nanodust particles confined in a radio frequency plasma. Simultaneous measurements of the dust properties, grain size and density, as well as the wave parameters, frequency and wave number, allow for an estimate of the ion density, ion drift velocity, and the dust charge using a hybrid model for the wave dispersion. It appears that the charge on the dust grains in the cloud is drastically reduced to tens of elementary charges compared with isolated dust particles in a plasma. The charge is much higher at the cloud's periphery, i.e., towards the void in the plasma center and also towards the outer edge of the cloud. [ABSTRACT FROM AUTHOR]

Nanodust is produced in an rf-driven push-pull parallel-plate reactor using argon with an acetylene admixture at 5-30 Pa. A scheme for the preparation of nanodust clouds with particle radii up to 400 nm for investigations in magnetized plasmas is proposed. The confinement that keeps the nanodust of different radii inside a moderately magnetized discharge (B ≤ 500 mT) is investigated by a comparison of 2d-Langmuir probe measurements in the dust-free plasma without and with a magnetic field and by the analysis of scattered light of nanodust clouds. It is shown that the dust cloud changes its shape when the dust density changes. This results in a reversed α -γ transition from a dense dust cloud with a central disk-like void to a dilute dust cloud with a toroidal void. When the dust density is further reduced, filaments are observed in the central part of the cloud, which were absent in the high-density phase. It is concluded that the dense nanodust cloud is able to suppress plasma filamentation in magnetized plasmas. [ABSTRACT FROM AUTHOR]