Plasma flow around and charge distribution of a dust cluster in a rf discharge

Abstract

We employ a particle-in-cell Monte Carlo collision/particle-particle particle-mesh (PIC-MCC/PPPM) simulation to study the plasma flow around and the charge distribution of a threedimensional dust cluster in the sheath of a low-pressure rf argon discharge. The geometry of the cluster and its position in the sheath are fixed to the experimental values, prohibiting a mechanical response of the cluster. Electrically, however, the cluster and the plasma environment, mimicking also the experimental situation, are coupled self-consistently. We find a broad distribution of the charges collected by the grains. The ion flux shows on the scale of the Debye length strong focusing and shadowing inside and outside the cluster due to the attraction of the ions to the negatively charged grains whereas the electron flux is characterized on this scale only by a weak spatial modulation of its magnitude depending on the rf phase. On the scale of the individual dust potentials, however, the electron flux deviates in the vicinity of the cluster strongly from the laminar flow associated with the plasma sheath. It develops convection patterns to compensate for the depletion of electrons inside the dust cluster.

Dusty (complex) plasmas—routes towards magnetized and polydisperse systems

“…The reason is that the particle experiences a higher flow of ions in the wakefield that leads to partial decharging of the particle. This effect has been found in simulations and has been confirmed in experiments [17,18,56,70,[81][82][83]. is the Wigner-Seitz radius and is a measure of the mean interparticle distance.…”

Continuum modelling of an asymmetric CCRF argon plasma reactor: Influence of higher excited states and sensitivity to model parameters

“…This is commonly seen for the metastable argon species 1 s 5 and 1 s 3 , [ 29 ] which are grouped as the metastable species Ar m . [ 12,13,30 ] Higher excited 2 p states (2 p 10 through 2 p 1 ) are often omitted from argon plasma models [ 9,17,31–34 ] ; however, they may also be grouped together with the metastable species [ 35–37 ] or represented as separate grouped processes. [ 30,38–41 ] The wide variability in choice of grouping, along with the cross‐section data chosen to represent these grouped processes, makes it difficult for readers to understand exactly which processes are represented in any given model.…”

“…The threshold energies for these grouped processes are listed in Table 2, and they were taken from the lowest threshold energy in the group. Superelastic collisions with electronically excited argon species are omitted in References [17,35,37,38] and included (typically for metastable species only) in References [12,13,30–33,36,39–41]. In the current study, superelastic collisions with excited species are only included for the metastable Ar m , using the principle of detailed balancing.…”

PIC Simulations of the MS4 Thruster

“…Within the group there exist also 1D3V and 3D3V PIC models, where the routines share a common ancestor for particle push, boundary and collision handling. A 3D3V version is designed to calculate even dusty plasmas [20] and has been able to reproduce their complex behavior [21]. The 1D3V model was applied to study two experimentally observed electronegative modes in capacitively coupled rf plasmas [22].…”