Preparation of magnetized nanodusty plasmas in a radio frequency-driven parallel-plate reactor

Abstract

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.

In-situ analysis of optically thick nanoparticle clouds

“…At this critical radius the particles leave the plasma confinement because the ion drag force and/or the gravitational force are larger than the confining electric field force. This also causes the formation of a void, a dust-free region in the center of the plasma [15,16].…”

Nanoparticle forming reactive plasmas: a multidiagnostic approach

“…As mentioned above, a region with high emission intensity in the centre of the plasma bulk was not observed during phase II. In several other studies the emission profile typical for the γ-regime has been observed [56,116,161]. The presence of this region with high emission intensity in the plasma bulk has been linked to the formation of a void inside the plasma bulk [56,105].…”

“…In the future, the list of diagnostics installed on the 'Pequod'-reactor should be extended. Especially self-excited electron resonance spectroscopy (SEERS) [189], Mie elliposmetry [122,173,174], a laser fan for light scattering [101,103,116], 132 CHAPTER 5. SUMMARY AND OUTLOOK infrared absorption spectroscopy [190,191], and near-edge x-ray absorption fine structure (NEXAFS) [123] are promising candidates.…”

“…The lack of precursor molecules suppresses further nucleation events could be verified by passing a laser fan through the discharge and detecting the scattered laser light (cf. for example [103,[115][116][117]).…”

The magnetized dusty plasma experiment (MDPX)

“…How is the dust grain charge affected by the magnetic field? However, in the majority of experiments, including those studies involving weakly magnetized plasmas (Kaw et al 2002;Vasil'ev et al 2007;Pilch et al 2008;Puttscher and Melzer 2014;Tadsen et al 2014), the dust grain charge most frequently inferred from measurements of the plasma parameters and using various charging models to estimate the value of the charge. How are the inter-dust forces modified by the magnetic field?…”